From brown@ncoast.org Sun Jun 26 14:54:01 1994 Newsgroups: comp.os.msdos.programmer,comp.answers,news.answers From: brown@ncoast.org (Stan Brown) Subject: comp.os.msdos.programmer FAQ Date: Thu, 23 Jun 1994 12:56:28 GMT Summary: This article contains questions that are frequently asked by DOS programmers, with tested answers. Please read it before posting questions or answers. Reply-To: brown@ncoast.org Followup-To: comp.os.msdos.programmer Organization: nej tak! Supersedes: Archive-name: msdos-programmer-faq/faq Comp-os-msdos-programmer-archive-name: dos-faq Posting-frequency: monthly Last-modified: 22 Jun 1994 Copyright (C) 1994 Stan Brown, Oak Road Systems. All rights reserved. This article is not in the public domain, but it may be redistributed so long as this notice, the acknowledgments, and the information on obtaining the latest copy of this list are retained and no fee is charged. The code fragments may be used freely; credit would be polite. Special note: Maintenance on this file is minimal because I have limited time (and, lately, limited interest) in this area. Someone with a more active interest in DOS programming could do the net a great service by taking over this list; send me email if interested. Subject: Table of Contents section 0. Introduction to this article 001. What is this article? (rev: 19 Apr 1994) 002. Why is this article? (rev: 20 Mar 1994) 003. How can I search this article for a particular topic? (rev: 20 Mar 1994) 004. Who has contributed to this article? 005. Are the answers guaranteed correct and complete? (rev: 20 Mar 1994) section 1. General questions 101. Why won't my code work? 102. What is this newsgroup about? (rev: 11 Sep 1993) 103. Is comp.os.msdos.programmer just for C programmers? (rev: 20 Mar 1994) 104. What's the difference from comp.sys.ibm.pc.programmer? 105. Is comp.os.msdos.programmer available as a mailing list? (new: 2 Feb 1993) 106. What's this "netiquette"? (rev: 20 Mar 1994) 107. How can I learn more about Usenet? (new: 7 Aug 1993) 108. What other technical newsgroups should I know about? (rev: 6 Apr 1994) section 2. Compile and link 201. What the heck is "DGROUP > 64K"? (rev: 18 Apr 1993) 202. How do I fix "automatic data segment exceeds 64K" or "stack plus data exceed 64K"? 203. Will Borland C code and Microsoft C code link together? (rev: 15 Aug 1993) 204. Why did my program bomb at run time with "floating point formats not linked" or "floating point not loaded"? (rev: 20 March 1994) 205. How can I change the stack size in Borland's C compilers? (rev: 24 March 1994) 206. What's the format of an .OBJ file? (rev: 24 Mar 1994) 207. What's the format of an .EXE header? 208. What's the difference between .COM and .EXE formats? section 3. Keyboard 301. How can I read a character without echoing it to the screen, and without waiting for the user to press the Enter key? 302. How can I find out whether a character has been typed, without waiting for one? 303. How can I disable Ctrl-C/Ctrl-Break and/or Ctrl-Alt-Del? (rev: 11 Sep 1993) 304. How can I disable the print screen function? 305. How can my program turn NumLock (CapsLock, ScrollLock) on or off? 306. How can I speed up the keyboard's auto-repeat? (rev: 24 Mar 1994) 307. What is the SysRq key for? 308. How can my program tell what kind of keyboard is on the system? 309. How can I tell if input, output, or stderr has been redirected? (rev: 24 Mar 1994) 310. How can I increase the size of the keyboard buffer? (new: 20 June 1993) 311. How can I stuff characters into the keyboard buffer? (new: 15 Aug 1993) section 4. Disks and files 401. What drive was the PC booted from? 402. How can I boot from drive b:? (rev: 24 Mar 1994) 403. Which real and virtual disk drives are valid? (rev: 15 Aug 1993) 404. How can I make my single floppy drive both a: and b:? 405. How can I disable access to a drive? (new: 15 Aug 1993) 406. How can a batch file test existence of a directory? (rev: 28 May 1994) 407. Why won't my C program open a file with a path? 408. How can I redirect printer output to a file? (rev: 16 Aug 1993) 409. How can I redirect the output of a batch file? (rev: 24 Mar 1994) 410. How can I redirect stderr? (rev: 24 Mar 1994) 411. How can my program open more files than DOS's limit of 20? (rev: 12 Sep 1993) 412. How can I read, create, change, or delete the volume label? 413. How can I get the disk serial number? (rev: 6 Jun 1994) 414. What's the format of .OBJ, .EXE., .COM files? 415. How can I flush the software disk cache? section 5. Serial ports (COM ports) 501. How do I set my machine up to use COM3 and COM4? 502. How do I find the I/O address of a COM port? (rev: 24 Mar 1994) 503. But aren't the COM ports always at I/O addresses 3F8, 2F8, 3E8, and 2E8? 504. How do I configure a COM port and use it to transmit data? (rev: 17 Sep 1993) section 6. Other hardware questions and problems 601. Which 80x86 CPU is running my program? (rev: 24 Mar 1994) 602. How can a C program send control codes to my printer? 603. How can I redirect printer output to a file? 604. Which video adapter is installed? 605. How do I switch to 43- or 50-line mode? 606. How can I find the Microsoft mouse position and button status? 607. How can I access a specific address in the PC's memory? (rev: 6 Jun 1994) 608. How can I read or write my PC's CMOS memory? (rev: 24 Mar 1994) 609. How can I access memory beyond 640K? (rev: 24 Mar 1994) section 7. Other software questions and problems 701. How can a program reboot my PC? (rev: 24 Mar 1994) 702. How can I time events with finer resolution than the system clock's 55 ms (about 18 ticks a second)? (rev: 24 Mar 1994) 703. How can I find the error level of the previous program? (rev: 24 Mar 1994) 704. How can a program set DOS environment variables? (rev: 24 Mar 1994) 705. How can I change the switch character to - from /? (rev: 20 Mar 1994) 706. How can I write a TSR (terminate-stay-resident utility)? (rev: 24 Mar 1994) 707. Why does my interrupt function behave strangely? (rev: 24 Sep 1993) 708. How can I write a device driver? 709. What can I use to manage versions of software? (rev: 21 Aug 1993) 710. What's this "null pointer assignment" after my C program executes? (rev: 20 Mar 1994) 711. How can a batch file tell whether it's being run in a DOS box under Windows? (new: 20 Mar 1994) 712. How can my program tell if it's running under Windows? (rev: 20 Mar 1994) 713. How can a program tell whether ANSI.SYS is installed? (new: 20 Apr 1994) 799. How do I copyright software that I write? (rev: 9 Sep 1993) section A. Downloading A01. What are SimTel, Garbo, and wustl? (rev: 6 Apr 1994) A02. I have no ftp access. How can I get files from the archives? (rev: 14 June 1993) A03. Can I get archives on CD-ROM? (rev: 24 May 1993) A04. Where do I find program ? (rev: 7 Aug 1993) A05. How can I check SimTel or Garbo before I post a request for a program? (rev: 24 Mar 1994) A06. How do I download and decode a program I found? (rev: 7 Aug 1993) A07. Where is UUDECODE? A08. Why do I get errors when extracting from a ZIP file I downloaded? (rev: 20 Mar 1994) section B. Vendors and products B01. How can I contact Borland? (rev: 6 Sep 1993) B02. How can I contact Microsoft? (rev: 18 Sep 1993) B03. What's the current version of UNZIP? (rev: 17 Mar 1994) B04. What is the phone number for a vendor's BBS? (rev: 24 Mar 1994) section C. More information C01. Are there any good on-line references for PC hardware components? (rev: 28 July 1993) C02. Are there any good on-line references for PC interrupts? C03. What and where is "Ralf Brown's interrupt list"? (rev: 6 Jun 1994) C04. Where can I find lex, yacc, and language grammars? C05. What's the best book to learn programming? C06. Where are FAQ lists archived? (rev: 29 Mar 1994) C07. Where can I get the latest copy of this FAQ list? (rev: 30 Mar 1994) C08. How do I use ftp? (rev: 6 Apr 1994) section 0. Introduction to this article ======================================= Subject: 001. What is this article? (rev: 19 Apr 1994) This is the FAQ list (Frequently Asked Questions list) for the newsgroup comp.os.msdos.programmer. Starting 2 Feb 1993, new questions and questions with revised answers are marked with "new:" or "rev:" and the change date. A separate article, containing just the changes, is posted with subject line "comp.os.msdos.programmer FAQ diffs". If the posting date shown above is much more than a month in the past, see "C07. Where can I get the latest copy of this FAQ list?" Subject: 002. Why is this article? (rev: 20 Mar 1994) FAQ lists are intended to reduce the noise level in their newsgroups that results from the repetition of the same questions, correct answers, wrong answers, corrections to the wrong answers, corrections to the corrections, debate, etc. This list should serve as a repository of the canonical "best" answers to the questions in it. The names of folks who have helped to improve this FAQ list are listed in "004. Who has contributed to this article?" Subject: 003. How can I search this article for a particular topic? (rev: 20 Mar 1994) This list is in digest format. To skip one topic and go to the next: Search for "Subject" starting in column 1. In trn and similar newsreaders, the command "g^Subject", or a simple Ctrl-G, does that. To search for specific topics: In the Table of Contents (above), locate the question you need. Then search for that question number. For example, while you're reading this list, the trn newsreader command "g 203" (note the two spaces) goes to question 203. If your newsreader doesn't support searches, you can extract these articles to a file and use your favorite editor's search commands. Subject: 004. Who has contributed to this article? This list is edited by Stan Brown, Oak Road Systems, Cleveland, Ohio, the "I" or "me" in some answers. Many articles posted in comp.os.msdos.programmer sparked ideas or provided information for the first version of this list. Though they are not responsible for any errors, thanks are due to the following persons for posted articles or private email that led to improvements in this FAQ list: Jamshid Afshar, Mark Aitchison, Sanjay Aiyagari, George Almasi, Aaron Auseth, Robert Baker, Preston Bannister, Scott Barman, Denis Beauregard, Per Bergland, Mike Black, Chris Blum, Ron Bodkin, Mark Brader, Jon Brinkmann, Andrew James Bromage, Glynn Brooks, Paul Brooks, Ralf Brown, Shaun Burnett, D'Arcy J.M. Cain, Raymond Chen, Denny de Jonge, Eric DeVolder, Alan Drew, Paul Ducklin, Gary Dueck, Roland Eriksson, Mark Evans, Markus Fischer, George Forsman, Roger Fulton, Vincent Giovannone, Robert Grunloh, B.Haible, Janos Haide, Klaus Hartnegg, Kris Heidenstrom, Tom Haapanen, Joel Hoffman, Ari Hovila, Chin Huang, Joe Huffman, Michael Holin, Mike Iarrobino, Byrial Jensen, Rune Jorgensen, Ajay Kamdar, Everett Kaser, Jeff Kellam, Jen Kilmer, Reinhard Kirchner, Dave Kirsch, Chad Knudsen, Samuel Ko, Janne Kukonlehto, Benjamin Lee, Stephen Lee, Jim Lynch, Greg Malknecht, Sidney Markowitz, Jim Marks, Dimitri Matzarakis, Fred McCall, Ken McKee, Doug Merrett, Tom Milner, Bill Moore, Duncan Murdoch, Steve Murphy, Daniel Neri, Mert Nickerson, David Nugent, John Oldenburg, David Pape, Keith Petersen, Karl Riedling, Arthur Rubin, Gerald Ruderman, Timo Salmi, Tapio Sand, John Schmid, Russell Schulz, Huseyin Sevay, Ajay Shah, Bob Smith, Sean Sullivan, Steve Summit, Tom Swingle, Anders Thulin, Curt Tilmes, Rick Watkins, Ya-Gui Wei, Joe Wells, Scott Winder, Gregory Youngblood, khill@vax1.umkc.edu New contributor: D'Arcy J.M. Cain, Janne Kukonlehto, Sean Sullivan Subject: 005. Are the answers guaranteed correct and complete? (rev: 20 Mar 1994) I've tried to check all facts, but THERE IS NO WARRANTY ON THE CODE OR ON THE TECHNIQUES DESCRIBED HEREIN. Please send corrections to brown@ncoast.org. All the code has been tested; but the testing may not have been perfect, and machines and configurations vary. (Except where otherwise noted, C code was tested with both BC++ 2.0 and MSC 5.0.) The mention of particular books or programs must not be construed to reflect unfavorably on any that are not mentioned. section 1. General questions ============================ Subject: 101. Why won't my code work? First you need to try to determine whether the problem is in your use of the programming language or in your use of MS-DOS and your PC hardware. (Your manual should tell you which features are standard and which are vendor- or MS-DOS- or PC-specific. You _have_ read your manual carefully, haven't you?) If the feature that seems to be working wrong is something related to your PC hardware or to the internals of MS-DOS, this group is the right place to ask. (Please check this FAQ list first, to make sure your question isn't already answered here.) On the other hand, if your problem is with the programming language, the comp.lang hierarchy (including comp.lang.pascal and comp.lang.c) is probably a better resource. Please read the other group's FAQ list thoroughly before posting. (These exist in comp.lang.c, comp.lang.c++, comp.lang.modula3, comp.lang.lisp, comp.lang.perl; they may exist in other groups as well.) It's almost never a good idea to crosspost between comp.os.msdos.programmer and a language group. Before posting in either place, try to make your program as small as possible while still exhibiting the bad behavior. Sometimes this alone is enough to show you where the trouble is. Also edit your description of the problem to be as short as possible. This makes it look more like you tried to solve the problem on your own, and makes people more inclined to try to help you. See also "106. What's this "netiquette"?" Subject: 102. What is this newsgroup about? (rev: 11 Sep 1993) comp.os.msdos.programmer (comp.sys.ibm.pc.programmer until September 1990) concerns programming for MS-DOS systems. The article "USENET Readership report for Aug 93" in news.lists shows 78,000 readers of this newsgroup worldwide. Traffic (exclusive of crossposts) was 813 articles aggregating 1604 Kbytes. Much of our traffic is about language products (chiefly from Borland and Microsoft). More programming topics focus on C than on any one other language, but we are not just for C programmers (see "103. Is comp.os.msdos.programmer just for C programmers?"). Since most MS-DOS systems run on hardware that is roughly compatible with the IBM PC, on Intel 8088, 80188, or 80x86 chips, we tend to get a lot of questions and answers about programming other parts of the hardware. Subject: 103. Is comp.os.msdos.programmer just for C programmers? (rev: 20 Mar 1994) No, it is for all programmers who want to share information about programming in MS-DOS and DOS replacements like 4DOS. Programs and questions are also posted in Pascal, assembly, and other languages (including MS-DOS batch programming.) Why does the newsgroup seem to be so C-oriented sometimes? There are two reasons. First, comp.lang.c and comp.lang.pascal have evolved in different directions. comp.lang.pascal welcomes vendor- specific discussion, such as Turbo Pascal. Since so many of TP's features are tailored to programming on PCs and in MS-DOS, Turbo Pascal programmers tend to find DOS questions welcomed there, so that comp.os.msdos.programmer gets less of the "DOS in Turbo Pascal" traffic. On the other hand, comp.lang.c has stayed closer to talking only about the C language, and vendor-specific or operating- system-specific questions are not welcome. This tends to push questions about disks, DOS file structure, video, the keyboard, TSRs, etc. to comp.os.msdos.programmer even when those programs are written in C. This FAQ is definitely C-oriented, not because that's necessarily best but because I tried to stick to what I could verify personally. As a C programmer (with some assembler), I could most carefully verify solutions in C or assembler. I felt that short, clear programs could be published in just one language and programmers could translate them into their languages of choice. But the FAQ list also contains several long programs written only in C; this is a defect with no obvious remedy. Most answers that point to source code at archive sites include both C- and Pascal-language source when available. Subject: 104. What's the difference from comp.sys.ibm.pc.programmer? c.s.i.p.programmer is the old name of comp.os.msdos.programmer, and has been obsolete since September 1990. However, many systems have not removed the old group, or have removed it but aliased it to the new name. This means that some people still think they're posting to c.s.i.p.programmer even though they're actually posting to comp.os.msdos.programmer. You can easily verify the non-existence of c.s.i.p.programmer by reference to the "List of Active Newsgroups" posted to news.groups. It's available as /pub/usenet/news.answers/active-newsgroups/part1 from the archives (see "C06. Where are FAQ lists archived?"). Subject: 105. Is comp.os.msdos.programmer available as a mailing list? (new: 2 Feb 1993) Sorry, no. Subject: 106. What's this "netiquette"? (rev: 20 Mar 1994) Netiquette is good Usenet etiquette. It includes basic rules like the ones below. (See also "107. How can I learn more about Usenet?") - Always read a newsgroup for a reasonable time before you post an article to it. - Pick the one right group for your article; don't crosspost unless absolutely necessary. If you absolutely must post an article to more than one group, do crosspost it and don't post the same article separately to each group. See "108. What other technical newsgroups should I know about?" when considering where to post an article. - Before you post a question, make sure you're posting to the right newsgroup; the best way to do that is to observe the preceding rule. Check the group's FAQ list (if it has one) to make sure that your question isn't already answered there; see "C06. Where are FAQ lists archived?". - When you post a question, if you ask for email responses then promise to post a summary. Keep your promise. And make it a real summary: don't just append all the email you got. Instead, write your own (brief) description of the solution: this is the best way to make sure you really understand it. - Before you post a follow-up, read the other follow-ups. Very often you'll find that someone else has already made the point you had in mind. - When someone posts a question, if you want to know the answer don't post a "me, too". Instead send email to the poster asking him or her to share responses with you. - When posting a follow-up to another posted article, remove all headers and signature lines from the old article; just keep the line "In
, so-and-so writes:". Also cut the original article down as much as possible; just keep enough of it to remind readers of the context. - Keep lines in posted articles to 72-75 characters. Many newsreaders chop off column 81 or arbitrarily insert a newline there, which makes longer lines difficult or impossible to read. But you need to keep well below 80 characters per line to allow for the > characters that get inserted when other people post follow-ups to your article. - Keep your signature to 4 lines or less (including any graphics), and for heaven's sake make sure it doesn't get posted twice in your article. - Don't post email without first obtaining the permission of the sender. Subject: 107. How can I learn more about Usenet? (new: 7 Aug 1993) There are two important newsgroups for learning about how Usenet and newsreader software works: - news.announce.newusers contains periodic postings that everybody is asked to read before posting anything to Usenet. (In theory, all new users are subscribed to news.announce.newusers automatically. But in practice not all newsreader software does that, so that many people violate the guidelines given there simply because they don't know about them.) - news.newusers.questions is described as "Q & A for users new to the Usenet". But new and long-time users can ask or answer questions about Usenet and newsreader software there. There's an important article, "Welcome to news.newusers.questions! (weekly posting)", that everyone is asked to read before posting to news.newusers.questions. (See below for ways to get a copy of that article.) The following postings in news.announce.newusers might be considered the "mandatory course" for new users: Introduction to news.announce.newusers What is Usenet? Answers to Frequently Asked Questions Rules for posting to Usenet A Primer on How to Work With the Usenet Community Hints on writing style for Usenet Emily Postnews Answers Your Questions on Netiquette The articles mentioned above are downloadable via ftp from rtfm.mit.edu in the following files: /pub/usenet/news.answers/news-newusers-intro Welcome to news.newusers.questions! (weekly posting) /pub/usenet/news.answers/news-announce-intro/part1 Introduction to news.announce.newusers /pub/usenet/news.answers/what-is-usenet/part1 What is Usenet? /pub/usenet/news.answers/usenet-faq/part1 Answers to Frequently Asked Questions /pub/usenet/news.answers/posting-rules/part1 Rules for posting to Usenet /pub/usenet/news.answers/usenet-primer/part1 A Primer on How to Work With the Usenet Community /pub/usenet/news.answers/usenet-writing-style/part1 Hints on writing style for Usenet /pub/usenet/news.answers/emily-postnews/part1 Emily Postnews Answers Your Questions on Netiquette For rtfm.mit.edu instructions, see "C06. Where are FAQ lists archived?" Subject: 108. What other technical newsgroups should I know about? (rev: 6 Apr 1994) Caution: Some of these newsgroups have specialized charters; you'll probably get flamed (and deserve it) if you post to an inappropriate group. Most groups have FAQ lists that will tell you what's appropriate. Don't post a request for the FAQ list; instead, retrieve it yourself: see "C06. Where are FAQ lists archived?" - misc.forsale.computers.d and misc.forsale.computers.pc-clone are where you post notices of equipment, software, or computer books that you want to sell. Please don't post or crosspost those notices to comp.os.msdos.programmer. - comp.os.ms-windows.programmer.* groups (formerly part of comp.windows.ms.programmer): Similar to comp.os.msdos.programmer, but focus on programming for the MS-Windows platform. - comp.sys.ibm.pc.hardware is for more hardware-oriented discussions of the machines that run DOS. - the various comp.lang.* groups for articles and questions on the programming languages. Caution: some groups welcome discussions that are operating-system dependent or vendor specific; others do not. For example, comp.lang.c is definitely _not_ for questions about programming DOS or PC system features, even if the programs are written in C. On the other hand, comp.lang.pascal contains much discussion that is specific to Turbo Pascal. - comp.binaries.ibm.pc.wanted: AFTER you have looked in the other groups, this is the place to post a request for a particular binary program. - comp.archives.msdos.announce (moderated) explains how to use the archive sites, especially Garbo and SimTel, and lists files uploaded to them. Discussions belong in comp.archives.msdos.d, which replaced comp.binaries.ibm.pc.archives in December 1992. - MSDOS-Ann mailing list, for those who cannot subscribe to the comp.archives.msdos.announce newsgroup, lists SimTel and Garbo uploads in digest format. Instructions are downloadable as /pc/MSDOSANN.ZIP from Garbo /pub/msdos/info/msdosann.zip from SimTel. - comp.binaries.ibm.pc.d is for discussions about programs posted in comp.binaries.ibm.pc, and only those programs. This is a good place to report bugs in the programs, but not to ask where to find them (see cbip.wanted, above). cbip.d is NOT supposed to be a general PC discussion group. - comp.sources.misc: a moderated group for source code for many computer systems. It tends to get lots of Unix stuff, but you may also pick up some DOS-compatible code here. - alt.sources: an unmoderated group for source code. Guidelines are posted periodically. - comp.os.msdos.programmer.turbovision is specifically for programming in Turbo Vision. section 2. Compile and link =========================== Subject: 201. What the heck is "DGROUP > 64K"? (rev: 18 Apr 1993) This Q explains the problem; the next Q gives some remedies. DGROUP is a link-time group of data segments, and the compiler typically generates code that expects DS to be pointing to DGROUP. (Exception: Borland's huge model has no DGROUP.) Here's what goes into DGROUP: - tiny model (all pointers near): DGROUP holds the entire program. - small and medium models (data pointers near): DGROUP holds all globals and static variables including string literals, plus the stack and the heap. - large, compact, and huge models in Microsoft (data pointers far): DGROUP holds only initialized globals and static variables including string literals, plus the stack and the near heap. - large and compact models in Borland (data pointers far): DGROUP holds initialized and uninitialized globals and static variables including string literals, but not the stack or heap. - huge model in Borland (data pointers far): there is no DGROUP, so the 64K limit doesn't apply. In all of the above, which is to say all six models in Microsoft C and all but huge in Borland C, DGROUP is limited to 64K including string literals (which are treated as static data). This limitation is due to the Intel CPU's segmented architecture. For more information, see topics like "memory models" and "memory management" in the index of your compiler manual. Also see TI738.asc, downloadable as part of /pub/msdos/turbo-c/bchelp10.zip at SimTel /pc/turbopas/bchelp10.zip at Garbo, for an extended general discussion of memory usage in Borland C programs, of which much applies to any C compiler in DOS. Subject: 202. How do I fix "automatic data segment exceeds 64K" or "stack plus data exceed 64K"? These messages are a variation of "DGROUP > 64K". For causes, please see the preceding Q. If you get this error in tiny model, your program is simply too big and you must use a different memory model. If you get this link error in models S, C, M, L, or Microsoft's H, there are some things you can do. (This error can't occur in Borland's huge model.) If you have one or two big global arrays, simply declare them far. The compiler takes this to mean that any references to them will use 32-bit pointers, so they'll be in separate segments and no longer part of DGROUP. Or you can use the /Gt[number] option with Microsoft or -Ff[=size] with Borland C++ 2.0 and up. This will automatically put variables above a certain size into their own segments outside of DGROUP. Yet another option is to change global arrays to far pointers. Then at the beginning of your program, allocate them from the far heap (_fmalloc() in Microsoft, farmalloc() in Borland). Finally, you can change to huge model (with Borland compilers, not Microsoft). Borland's H model still uses far pointers by default, but "sets aside the [64K] limit" and has no DGROUP group, according to the BC++ 2.0 Programmer's Guide. Microsoft's H model does use huge data pointers by default but retains DGROUP and its 64K limit, so switching to the H model doesn't buy you anything if you have DGROUP problems. Subject: 203. Will Borland C code and Microsoft C code link together? (rev: 15 Aug 1993) Typically this question is asked by someone who owns compiler A and is trying to write code to link with a third-party library that was compiled under compiler B. The answer to the question is, Not in general. Here are some of the reasons: - "Helper" functions (undocumented functions for stack checking, floating-point arithmetic, and operations on longs) differ between the two compilers. - The compilers may embed instructions in the object code that tell the linker to look for their own run-time libraries. You can use the linker option that says to ignore such instructions: /n in TLINK, /NOD in the Microsoft linker (the one that comes with the C compiler, not the one that used to come with DOS). But getting around this problem will very likely just reveal other problems, like different helper functions, that have no easy solution. Those problems will generate link-time errors. Others may not show up until run time: - Borland's compact, large, and huge models don't assume DS=SS, but Microsoft's do. The -Fs option on the Borland compiler, or one of the /A options on Microsoft, should take care of this problem-- once you know that's what's going on. - Check conventions for ordering and packing structure members, and for alignment of various types on byte, word, paragraph, or other boundaries. Again, you can generally adjust your code to match if you know what conventions were used in compiling the "foreign" libraries. - Check the obvious and make sure that your code was compiled under the same memory model as the code you're trying to link with. (That's necessary, but no guarantee. Microsoft and Borland don't use exactly the same conventions for segments and groups, particularly in the larger memory models.) That said, there are some circumstances where you can link hybrids. Your best chance of success comes if you compile in large model with the compiler switch that says to reload DS on entry to each function, avoid longs and floating point, use only 16-bit pointers, suppress stack checking, and specify all libraries used in the link. Subject: 204. Why did my program bomb at run time with "floating point formats not linked" or "floating point not loaded"? (rev: 20 March 1994) These messages look similar but have very different causes. "floating point not loaded" is Microsoft C's run-time message when the code requires a numeric coprocessor but your computer doesn't have one installed. If the program is yours, relink it using the xLIBCE or xLIBCA library (where x is the memory model). "floating point formats not linked" is a Borland run-time error (Borland C or C++, Turbo C or C++). Borland's compilers try to be smart and not link in the floating-point (f-p) library unless you need it. Alas, they all get the decision wrong. One common case is where you don't call any f-p functions, but you have %f or other f-p formats in scanf() or printf() calls. The cure is to call an f-p function, or at least force one to be present in the link. To do that, define this function somewhere in a source file but don't call it: static void forcefloat(float *p) { float f = *p; forcefloat(&f); } It doesn't have to be in the module with the main program, as long as it's in a module that will be included in the link. If you have Borland C++ 3.0, the README file documents a slightly less ugly work-around. Insert these statements in your program: extern unsigned _floatconvert; #pragma extref _floatconvert Subject: 205. How can I change the stack size in Borland's C compilers? (rev: 24 March 1994) In Turbo C, Turbo C++, and Borland C++, you may not find "stack size" in the index but the global variable _stklen should be there. The manual will instruct you to put a statement like extern unsigned _stklen = 54321U; in your code, outside of any function. You must assign the value right in the extern statement; it won't work to assign a value at run time. The linker may give you a duplicate symbol warning, which you can ignore. Subject: 206. What's the format of an .OBJ file? (rev: 24 Mar 1994) - base .OBJ format: Intel's document number #121748-001, {8086 Relocatable Object Module Formats}. (not verified) Both Microsoft and Borland have extended the .OBJ format, as has IBM for OS/2; and according to the MS-DOS encyclopedia, Microsoft doesn't actually use all the listed formats. - Microsoft-specific .OBJ formats: * The .OBJ format document dated 14 Dec 1992, a WinHelp file from the Microsoft developer's CD-ROM (266K after unzipping), is downloadable as /vendor/microsoft/developer-network/ctech/11-9.zip from ftp.uu.net. * A 45-page article can be found in the {MS-DOS Encyclopedia}, ISBN 1-55615-049-0, now out of print. * "Microsoft Object Module Format (OMF)" Specification, 22 Nov 1991, was published by the Microsoft Languages Group. (not verified) - Borland-specific .OBJ formats: Open Architecture Handbook. The Borland Developer's Technical Guide, 1991, no ISBN. Chapter 2, "Object file contents", (pages 27-50) covers the comment records sent to the object file by Borland C++ version 3.0 and other Borland compilers. The comment records mostly contain information for the Borland debugger. (not verified) - A "tutorial on the .OBJ format" comes with the VAL experimental linker, downloadable as /pub/msdos/pgmutil/val-link.zip at SimTel /pc/assembler/linker.zoo at Garbo. Despite such different names, those files have the same contents, but their contents are dated 18 Feb 1989. You'd be better off with one of the more recent references listed above. Subject: 207. What's the format of an .EXE header? See PC Magazine 30 June 1992 (xi:12) pages 349-350 for the old and new formats. For a more detailed layout, look under INT 21 AH=4B in Ralf Brown's interrupt list (Q C03). That list includes extensions for Borland's TLINK and Borland debugger info. Among the books that detail formats of executable files are {DOS Programmer's Reference: 2d Edition} by Terry Dettman and Jim Kyle, ISBN 0-88022-458-4; and {Microsoft MS-DOS Programmer's Reference}, ISBN 1-55615-329-5. Subject: 208. What's the difference between .COM and .EXE formats? To oversimplify: a .COM file is a direct image of core, and an .EXE file will undergo some further relocation when it is run (and so it begins with a relocation header). A .COM file is limited to 64K for all segments combined, but an .EXE file can have as many segments as your linker will handle and be as large as RAM can take. The actual file extension doesn't matter. DOS knows that a file being loaded is in .EXE format if its first two bytes are MZ or ZM; otherwise it is assumed to be in .COM format. For instance, DR-DOS 6.0's COMMAND.COM is in .EXE format. section 3. Keyboard =================== Subject: 301. How can I read a character without echoing it to the screen, and without waiting for the user to press the Enter key? The C compilers from Microsoft and Borland offer getch() (or getche() to echo the character); Turbo Pascal has ReadKey. In other programming languages, execute INT 21 AH=8; AL is returned with the character from standard input (possibly redirected). If you don't want to allow redirection, or you want to capture Ctrl-C and other special keys, use INT 16 AH=10; this will return the scan code in AH and ASCII code (if possible) in AL, but AL=E0 with AH nonzero indicates that one of the grey "extended" keys was pressed. (If your BIOS doesn't support the extended keyboard, use INT 16 AH=0 not 10.) Subject: 302. How can I find out whether a character has been typed, without waiting for one? In Turbo Pascal, use KeyPressed. Both Microsoft C and Turbo C offer the kbhit() function. All of these tell you whether a key has been pressed. If no key has been pressed, they return that information to your program. If a keystroke is waiting, they tell your program that but leave the key in the input buffer. You can use the BIOS call, INT 16 AH=01 or 11, to check whether an actual keystroke is waiting; or the DOS call, INT 21 AH=0B, to check for a keystroke from stdin (subject to redirection). See Ralf Brown's interrupt list (Q C03). Subject: 303. How can I disable Ctrl-C/Ctrl-Break and/or Ctrl-Alt-Del? (rev: 11 Sep 1993) Several utilities are downloadable from /pub/msdos/keyboard at SimTel. In that directory, cadel.zip contains a TSR (with source code) to disable those keys. Also, keykill.arc contains two utilities: keykill.com lets you disable up to three keys of your choice, and deboot.com changes the boot key to leftShift-Alt-Del. C programmers who simply want to make sure that the user can't Ctrl- Break out of their program can use the ANSI-standard signal() function; the Borland compilers also offer ctrlbrk() for handling Ctrl-Break. However, if your program uses normal DOS input such as getch(), ^C will appear on the screen when the user presses Ctrl-C or Ctrl-Break. You can avoid the ^C echo for Ctrl-C by using _bios_keybrd() in MSC or bioskey() in BC++; however, Ctrl-Break will still terminate the program. An alternative approach involves programming input at a lower level. You can use INT 21 AH=7, which allows redirection but doesn't echo the ^C (or any other character, for that matter); or use INT 16 AH=0 or 10; or hook INT 9 to discard Ctrl-C and Ctrl-Break before the regular BIOS keyboard handler sees them; etc., etc. You should be aware that Ctrl-C and Ctrl-Break are processed quite differently internally. Ctrl-Break, like all keystrokes, is processed by the BIOS code at INT 9 as soon as the user presses the keys, even if earlier keys are still in the keyboard buffer: by default the handler at INT 1B is called. Ctrl-C is not special to the BIOS, nor is it special to DOS functions 6 and 7; it _is_ special to DOS functions 1 and 8 when at the head of the keyboard buffer. You will need to make sure BREAK is OFF to prevent DOS polling the keyboard for Ctrl-C during non-keyboard operations. Some good general references are {Advanced MS-DOS} by Ray Duncan, ISBN 1-55615-157-8; {8088 Assembler Language Programming: The IBM PC}, ISBN 0-672-22024-5, by Willen & Krantz; and {COMPUTE!'s Mapping the IBM PC}, ISBN 0-942386-92-2. Subject: 304. How can I disable the print screen function? There are really two print screen functions: 1) print current screen snapshot, triggered by PrintScreen or Shift-PrtSc or Shift- grey*, and 2) turn on continuous screen echo, started and stopped by Ctrl-P or Ctrl-PrtSc. 1) Screen snapshot to printer The BIOS uses INT 5 for this. Fortunately, you don't need to mess with that interrupt handler. The standard handler, in BIOS versions dated December 1982 or later, uses a byte at 0040:0100 (= 0000:0500) to determine whether a print screen is currently in progress. If it is, pressing PrintScreen again is ignored. So to disable the screen snapshot, all you have to do is write a 1 to that byte. When the user presses PrintScreen, the BIOS will think that a print screen is already in progress and will ignore the user's keypress. You can re- enable PrintScreen by zeroing the same byte. Here's some simple code: void prtsc_allow(int allow) /* 0=disable, nonzero=enable */ { unsigned char far* flag = (unsigned char far*)0x00400100UL; *flag = (unsigned char)!allow; } 2) Continuous echo of screen to printer If ANSI.SYS is loaded, you can easily disable the continuous echo of screen to printer (Ctrl-P or Ctrl-PrtSc). Just redefine the keys by "printing" strings like these to the screen (BASIC print, C printf(), Pascal Write statements, or ECHO command in batch files), where <27> stands for the Escape character, ASCII 27: <27>[0;114;"Ctrl-PrtSc disabled"p <27>[16;"^P"p If you haven't installed ANSI.SYS, I can't offer an easy way to disable the echo-screen-to-printer function. Actually, you might not need to disable Ctrl-P and Ctrl-PrtSc. If your only concern is not locking up your machine, when you see the "Abort, Retry, Ignore, Fail" prompt just press Ctrl-P again and then press I. As an alternative, install one of the many print spoolers that intercept printer-status queries and always return "Printer ready". Subject: 305. How can my program turn NumLock (CapsLock, ScrollLock) on or off? First, if you just don't want NumLock turned on when you reboot, check your system's setups. (Use Ctrl-Alt-Enter any time, or press a special key like Del at boot time, or run the setup program supplied with your system.) Many systems now have an option in setup to turn NumLock off at boot time. You need to twiddle bit 5, 6, or 4 of location 0040:0017. Here's some code: lck() turns on a lock state, and unlck() turns it off. (The status lights on some keyboards may not reflect the change. If yours is one, call INT 16 AH=2, "get shift status", and that may update them. It will certainly do no harm.) #define NUM_LOCK (1 << 5) #define CAPS_LOCK (1 << 6) #define SCRL_LOCK (1 << 4) void lck(int shiftype) { char far* kbdstatus = (char far*)0x00400017UL; *kbdstatus |= (char)shiftype; } void unlck(int shiftype) { char far* kbdstatus = (char far*)0x00400017UL; *kbdstatus &= ~(char)shiftype; } Subject: 306. How can I speed up the keyboard's auto-repeat? (rev: 24 Mar 1994) The keyboard speed has two components: delay (before a key that you hold down starts repeating) and typematic rate (the speed once the key starts repeating). Most BIOS versions since 1986 let software change the delay and typematic rate by calling INT 16 AH=3, "set typematic rate and delay"; see Ralf Brown's interrupt list (Q C03). If you have DOS 4.0 or later, you can use the MODE CON command that you'll find in your DOS manual. On 83-key keyboards (mostly XTs), the delay and typematic rate can't easily be changed. According to PC Magazine 15 Jan 1991 (x:1) page 409, to adjust the typematic rate you need "a memory-resident program which simply '[watches]' the keyboard to see if you're holding down a key ... and after a certain time [starts] stuffing extra copies of the held-down key into the buffer." No source code is given in that issue; but the QUICKEYS utility that PC Magazine published in 1986 does this sort of watching (not verified); source and object code are downloadable in /pub/msdos/pcmag/vol5n05.zip from SimTel. Subject: 307. What is the SysRq key for? There is no standard use for the key. The BIOS keyboard routines in INT 16 simply ignore it; therefore so do the DOS input routines in INT 21 as well as the keyboard routines in libraries supplied with high-level languages. When you press or release a key, the keyboard triggers hardware line IRQ1, and the CPU calls INT 9. INT 9 reads the scan code from the keyboard and the shift states from the BIOS data area. What happens next depends on whether your PC's BIOS supports an enhanced keyboard (101 or 102 keys). If so, INT 9 calls INT 15 AH=4F to translate the scan code. If the translated scan code is 54 hex (for the SysRq key) then INT 9 calls INT 15 AH=85 and doesn't put the keystroke into the keyboard buffer. The default handler of that function does nothing and simply returns. (If your PC has an older BIOS that doesn't support the extended keyboards, INT 15 AH=4F is not called. Early ATs have 84-key keyboards, so their BIOS calls INT 15 AH=85 but not 4F.) Thus your program is free to use SysRq for its own purposes, but at the cost of some programming. You could hook INT 9, but it's probably easier to hook INT 15 AH=85, which is called when SysRq is pressed or released. Subject: 308. How can my program tell what kind of keyboard is on the system? Ralf Brown's Interrupt List (Q C03) includes MEMORY.LST, a detailed breakdown by Robin Walker of the contents of the BIOS system block that starts at 0040:0000. Bit 4 of byte 0040:0096 is "1=enhanced keyboard installed". C code to test the keyboard type: char far *kbd_stat_byte3 = (char far *)0x00400096UL; if (0x10 & *kbd_stat_byte3) /* 101- or 102-key keyboard is installed */ PC Magazine 15 Jan 1991 (x:1) suggests on page 412 that "for some clones [the above test] is not foolproof". If you use this method in your program you should provide the user some way to override this test, or at least some way to tell your program to assume a non- enhanced keyboard. The article suggests a different approach to determining the type of keyboard. Subject: 309. How can I tell if input, output, or stderr has been redirected? (rev: 24 Mar 1994) Normally, input and output are associated with the console (i.e., with the keyboard and the screen, respectively). If either is not, you know that it has been redirected. Some source code to check this is available at the usual archive sites. If you program in Turbo Pascal, you'll want this downloadable collection of Turbo Pascal units: /pc/ts/tspa33*.zip at Garbo /pub/msdos/turbopas/tspa33*.zip at SimTel. (where the * is 70, 60, 55, 50, or 40 for Turbo Pascal 7.0, 6.0, 5.5, 5.0, or 4.0 respectively.) Source code is not included. Also see the downloadable Frequently Asked Questions files by Timo Salmi: /pc/ts/tsfaqp18.zip at Garbo /pub/msdos/info/tsfaqp18.zip at SimTel. If you program in C, use isatty() if your implementation has it. Otherwise, /pub/msdos/sysutil/is_con10.zip is downloadable from SimTel; it includes source code. Good references for the principles are PC Magazine 16 Apr 1991 (x:7) page 374; Ray Duncan's {Advanced MS-DOS}, ISBN 1-55615-157-8, or Ralf Brown's interrupt list (Q C03) for INT 21 AX=4400; and Terry Dettman and Jim Kyle's {DOS Programmer's Reference: 2d edition}, ISBN 0-88022-458-4, pages 602-603. Subject: 310. How can I increase the size of the keyboard buffer? (new: 20 June 1993) I tested only one of the many available device drivers that do this, namely BUF160, which extends the keyboard buffer to 160 characters. It performed flawlessly for two years with MS-DOS 5 and Windows 3.1. It's downloadable as /pub/msdos/keyboard/buf160_6.zip at SimTel /pc/keyboard/buf160_6.zip at Garbo. Subject: 311. How can I stuff characters into the keyboard buffer? (new: 15 Aug 1993) If your computer has an enhanced keyboard (see "308. How can my program tell what kind of keyboard is on the system?"), put the scan code in CH and the ASCII character in CL, then execute INT 16 AH=5. The return in AL is 0 for success or 1 for buffer full. section 4. Disks and files ========================== Subject: 401. What drive was the PC booted from? Under DOS 4.0 or later, use INT 21 AX=3305. DL is returned with an integer indicating the boot drive (1=A:, etc.). Subject: 402. How can I boot from drive b:? (rev: 24 Mar 1994) Downloadable shareware: /pub/msdos/diskutil/boot_b.zip from SimTel /pc/bootutil/boot_b.zip from Garbo. The included documentation says it works by writing a new boot sector on a disk in your a: drive that redirects the boot to your b: drive. (A similar utility is bboot.zip in the same directory at Garbo only.) If that doesn't work, you can always interchange your a: and b: drives by switching ribbon cables and changing the setup in your BIOS. From an article posted 27 Jan 1993 on another newsgroup: Take the "ribbon" connector, as you call it, and switch them. To double check, start at the end of the cable that connects to the motherboard or floppy controller. Follow the cable until you get to the first connector. Connect this to the drive you want to be b:. After this, there should be a few lines on the cable that get flipped left to right. (On most cables, they just cut the lines and physically reverse them. It should be quite obvious from looking at the cable.) Anyway, the connector after the pins get flipped right to left is the connector for your a: drive. Subject: 403. Which real and virtual disk drives are valid? (rev: 15 Aug 1993) Use INT 21 AH=29 (parse filename). Point DS:SI at a null-terminated ASCII string that contains the drive letter and a colon, point ES:DI at a 37-byte dummy FCB buffer, and call INT 21 AX=2900. On return, AL is FF if the drive is invalid, something else if the drive is valid. RAM disks and SUBSTed drives are considered valid. You can detect whether the drive is ASSIGNed by using INT 2F AX=0601. To check whether the drive is SUBSTed, use INT 21 AX=4409; or use INT 21 AH=52 to test for both JOIN and SUBST. See Ralf Brown's interrupt list (Q C03). Unfortunately, the b: drive is considered valid even on a single- diskette system. You can check that special case by interrogating the BIOS equipment byte at 0040:0010. Bits 7-6 contain the one less than the number of diskette drives, so if those bits are zero you know that b: is an invalid drive even though function 29 says it's valid. Following is some code originally posted by Doug Dougherty to test valid drives (treating SUBSTed and JOINed drives as valid), with my fix for the b: special case, tested in Borland C++ 2.0 (in the small model): #include #include void drvlist(void) { char *s = "A:", fcb_buff[37]; int valid; for ( ; *s<='Z'; (*s)++) { _SI = (unsigned) s; _DI = (unsigned) fcb_buff; _ES = _DS; _AX = 0x2900; geninterrupt(0x21); valid = _AL != 0xFF; if (*s == 'B' && valid) { char far *equipbyte = (char far *)0x00400010UL; valid = (*equipbyte & (3 << 6)) != 0; } printf("Drive '%s' is %sa valid drive.\n", s, valid ? "" : "not "); } } I translated this to MSC 7.0 and tested it in small model: #include #include void drvlist(void) { char *s = "A:", fcb_buff[37], *buff=fcb_buff; int valid; for ( ; *s<='Z'; (*s)++) { __asm mov si,s __asm mov di,buff __asm mov ax,ds __asm mov es,ax __asm mov ax,0x2900 __asm int 21h __asm xor ah,ah __asm mov valid,ax valid = (valid != 0xFF); if (*s == 'B' && valid) { char far *equipbyte = (char far *)0x00400010UL; valid = (*equipbyte & (3 << 6)) != 0; } printf("Drive '%s' is %sa valid drive.\n", s, valid ? "" : "not "); } } Subject: 404. How can I make my single floppy drive both a: and b:? Under any DOS since DOS 2.0, you can put the command assign b=a into your AUTOEXEC.BAT file. Then, when you type "dir b:" you'll no longer get the annoying prompt to insert diskette B (and the even more annoying prompt to insert A the next time you type "dir a:"). You may be wondering why anybody would want to do this. Suppose you use two different machines, maybe one at home and one at work. One of them has only a 3.5" diskette drive; the other machine has two drives, and b: is the 3.5" one. You're bound to type "dir b:" on the first one, and get the nuisance message Insert diskette for drive B: and press any key when ready. But if you assign drive b: to point to a:, you avoid this problem. Caution: there are a few commands, such as DISKCOPY, that will not work right on ASSIGNed or SUBSTed drives. See the DOS manual for the full list. Before typing one of those commands, be sure to turn off the mapping by typing "assign" without arguments. The DOS 5.0 manual says that ASSIGN is obsolete, and recommends the equivalent form of SUBST: "subst b: a:\". Unfortunately, if this command is executed when a: doesn't hold a diskette, the command fails. ASSIGN doesn't have this problem, so under DOS 5.0 you should disregard that particular bit of advice in the manual. Subject: 405. How can I disable access to a drive? (new: 15 Aug 1993) Reader Eric DeVolder writes that he has made available a program to do this. I haven't tried it, but it's downloadable as /pub/msdos/diskutil/rmdriv20.zip from SimTel /pc/sysutil/rmdriv20.zip at Garbo. Subject: 406. How can a batch file test existence of a directory? (rev: 28 May 1994) The standard way, which in fact is documented in the DOS manual, is if exist d:\path\nul goto found Unfortunately, this is not entirely reliable. I found it failed in Pathworks (a/k/a PCSA, DEC's network that connects PCs and VAXes), or on a MARS box that uses an OEM version of MS-DOS 5.0. Readers have reported that it gave the wrong answer on Novell networks, on DR-DOS, and in a DOS window under OS/2. By "failed" I mean that it "found" a directory that didn't exist, or failed to find one that did exist, or both. (I'm told that IBM fixed the OS/2 bug in version 2.11 of OS/2.) There appears to be no foolproof way to use pure batch commands to test for existence of a directory. The real solution is to write a program, which returns a value that your batch program can then test with an "if errorlevel". Reader Duncan Murdoch kindly posted the following Turbo Pascal version: program existdir; { Confirms the existence of a directory given on the command line. Returns errorlevel 2 on error, 1 if not found, 0 if found. } uses dos; var s : searchrec; begin if paramcount <> 1 then begin writeln('Syntax: EXISTDIR directory'); halt(2); end else begin findfirst(paramstr(1),Directory,S); while (Doserror = 0) and ((Directory and S.Attr) = 0) do findnext(S); if Doserror <> 0 then begin Writeln('Directory not found.'); halt(1); end else begin Writeln('Directory found.'); halt(0); end; end; end. Timo Salmi also has a Turbo Pascal version in his Turbo Pascal FAQ, which is downloadable as /pc/ts/tsfaqp18.zip at Garbo /pub/msdos/info/tsfaqp18.zip at SimTel. Subject: 407. Why won't my C program open a file with a path? You've probably got something like the following code: char *filename = "c:\foo\bar\mumble.dat"; FILE *fptr; . . . fptr = fopen(filename, "r"); The problem is that \f is a form feed, \b is a backspace, and \m is m. Whenever you want a backslash in a string constant in C, you must use two backslashes: char *filename = "c:\\foo\\bar\\mumble.dat"; This is a feature of every C compiler, because Dennis Ritchie designed C this way. It's a problem only on MS-DOS systems, because only DOS (and Atari ST/TT running TOS) uses the backslash in directory paths. But even in DOS this backslash convention applies _only_ to string constants in your source code. For file and keyboard input at run time, \ is just a normal character, so users running your program would type in file specs the same way as in DOS commands, with single \ characters. Another possibility is to code all paths in source programs with / rather than \ characters: char *filename = "c:/foo/bar/mumble.dat"; Ralf Brown writes, "All versions of the DOS kernel accept either forward or backslashes as directory separators. I tend to use this form more frequently than backslashes since it is easier to type and read." This applies to DOS function calls (and therefore to calls to the file library of every programming language), but not to DOS commands. Subject: 408. How can I redirect printer output to a file? (rev: 16 Aug 1993) Recommended: PRN2FILE from PC Magazine, downloadable as: /pub/msdos/printer/prn2file.zip at SimTel /pc/printer/prn2file.zip at Garbo. PC Magazine has given copies away as part of its utilities disks, so you may already have a copy. The directories mentioned above have lots of other utilities to redirect printer output. Subject: 409. How can I redirect the output of a batch file? (rev: 24 Mar 1994) Assuming the batch file is called batch.bat, to send its output (stdout) to another file, just invoke COMMAND.COM as a secondary command processor: command /c batch parameters_if_any >outfile Timo Salmi's notes on this and other batch tricks are downloadable: /pub/msdos/batutil/tsbat44.zip at SimTel /pc/ts/tsbat44.zip at Garbo. Subject: 410. How can I redirect stderr? (rev: 24 Mar 1994) Use freopen(..., stderr) and then execute the desired command via system(). There are downloadable versions of programs to do this. I recommend this file, which includes TP4 source and executable: /pub/msdos/sysutil/rdstderr.zip from SimTel. A C example is downloadable as /pub/msdos/c/redirect.c from SimTel. I compiled it with MSC 7.0, and it works fine with one exception: Contrary to the included comments, redirected output starts writing at the beginning of the output file rather than appending. That is easily solved by adding "fseek(stderr, 0L, SEEK_END);" after the freopen() call for stderr. Subject: 411. How can my program open more files than DOS's limit of 20? (rev: 12 Sep 1993) This is a summary of an article Ralf Brown posted on 8 August 1992, with some additions from a Microsoft tech note and information from Chin Huang.) DOS imposes some limits. Once you overcome those, which is pretty easy, you may have to take additional measures to overcome the limitations built into your compiler's run-time library. 1) Limitations imposed by DOS There are separate limits on files and file handles. For example, DOS opens three files but five file handles: CON (stdin, stdout, and stderr), AUX (stdaux), and PRN (stdprn). The limit in FILES= in CONFIG.SYS is a system-wide limit on files opened by all programs (including the three that DOS opens and any opened by TSRs); each process has a limit of 20 handles (including the five that DOS opens). Example: CONFIG.SYS has FILES=40. Then program #1 will be able to open 15 file handles. Assuming that the program actually does open 15 handles pointing to 15 different files, other programs could still open a total of 22 files (40-3-15 = 22), though no one program could open more than 15 file handles. If you're running DOS 3.3 or later, you can increase the per-process limit of 20 file handles by a call to INT 21 AH=67, Set Handle Count. Your program is still limited by the system-wide limit on open files, so you may also need to increase the FILES= value in your CONFIG.SYS file (and reboot). The run-time library that you're using may have a fixed-size table of file handles, so you may also need to get source code for the module that contains the table, increase the table size, and recompile it. 2) Limitations in Microsoft C run-time library In Microsoft C the run-time library limits you to 20 file handles. To change this, you must be aware of two limits: - file handles used with _open(), _read(), etc.: Edit _NFILE_ in CRT0DAT.ASM. - stream files used with fopen(), fread(), etc.: Edit _NFILE_ in _FILE.C for DOS or FILE.ASM for Windows/QuickWin. This must not exceed the value of _NFILE_ in CRT0DAT.ASM. (QuickWin uses the constant _WFILE_ in CRT0DAT.ASM and WFILE.ASM for the maximum number of child text windows.) After changing the limits, recompile using CSTARTUP.BAT. Microsoft recommends that you first read README.TXT in the same directory. 3) Limitations in Borland C++ run-time library (Reader Chin Huang provided this information on 12 Sep 1993.) To increase the open file limit for a program you compile with Borland C++ 3.1, edit the file _NFILE.H in the include directory and change the _NFILE_ value. Compile and link the modules FILES.C and FILES2.C from the lib directory into your program. Subject: 412. How can I read, create, change, or delete the volume label? In DOS 5.0 (and possibly in 4.0 as well), there are actually two volume labels: the LABEL command reports only the first but changes both of them. - The traditional volume label is an entry with "volume label" attribute in the root directory of the disk. The DIR, VOL, and LABEL commands report this volume label, and LABEL sets it. - There is a second volume label, which may be different, in the boot record along with the serial number. In DOS 4.0 and later, INT 21 AH=69 gets or sets the boot record's serial number and volume label together; see "413. How can I get the disk serial number?" DIR and VOL ignore this volume label; the LABEL command doesn't report it but does set it. The rest of this answer assumes that by "volume label" you mean the traditional one, the one that DIR and VOL display. Though it's a directory entry in the root directory, you can't change it using the newer DOS file-access functions (INT 21 AH=3C, 41, 43); instead, use the old FCB-oriented directory functions. Specifically, you need to allocate a 64-byte buffer and a 41- byte extended FCB (file control block). Call INT 21 AH=1A to find out whether there is a volume label. If there is, AL returns 0 and you can change the label using DOS function 17 or delete it using DOS function 13. If there's no volume label, function 1A will return FF and you can create a label via function 16. Important points to notice are that ? wildcards are allowed but * are not; the volume label must be space filled not null terminated. The following MSC 7.0 code worked for me in DOS 5.0; the functions it uses have been around since DOS 2.0. The function parameter is 0 for the current disk, 1 for a:, 2 for b:, etc. It doesn't matter what your current directory is; these functions always search the root directory for volume labels. (I didn't try to change the volume label of any networked drives.) // Requires DOS.H, STDIO.H, STRING.H void vollabel(unsigned char drivenum) { static unsigned char extfcb[41], dta[64], status, *newlabel; int chars_got = 0; #define DOS(buff,func) __asm { __asm mov dx,offset buff \ __asm mov ax,seg buff __asm push ds __asm mov ds,ax \ __asm mov ah,func __asm int 21h __asm pop ds \ __asm mov status,al } #define getlabel(buff,prompt) newlabel = buff; \ memset(newlabel,' ',11); printf(prompt); \ scanf("%11[^\n]%n", newlabel, &chars_got); \ if (chars_got < 11) newlabel[chars_got] = ' '; // Set up the 64-byte transfer area used by function 1A. DOS(dta, 1Ah) // Set up an extended FCB and search for the volume label. memset(extfcb, 0, sizeof extfcb); extfcb[0] = 0xFF; // denotes extended FCB extfcb[6] = 8; // volume-label attribute bit extfcb[7] = drivenum; // 1=A,2=B,...; 0=current drive memset(&extfcb[8], '?', 11);// wildcard *.* DOS(extfcb,11h) if (status == 0) { // DTA has volume label's FCB printf("volume label is %11.11s\n", &dta[8]); getlabel(&dta[0x18], "new label (\"delete\" to delete): "); if (chars_got == 0) printf("label not changed\n"); else if (strncmp(newlabel,"delete ",11) == 0) { DOS(dta,13h) printf(status ? "label failed\n" : "label deleted\n"); } else { // user wants to change label DOS(dta,17h) printf(status ? "label failed\n" : "label changed\n"); } } else { // no volume label was found printf("disk has no volume label.\n"); getlabel(&extfcb[8], "new label ( for none): "); if (chars_got > 0) { DOS(extfcb,16h) printf(status ? "label failed\n" : "label created\n"); } } } // end function vollabel Subject: 413. How can I get the disk serial number? (rev: 6 Jun 1994) If the disk was formattted by DOS 4.0 or later, use INT 21: AX=6900 gets the serial number; AX=6901 sets it. (The disk serial number doesn't exist if the disk was formatted with an earlier version of DOS, or with some third-party formatters.) See Ralf Brown's interrupt list (Q C03), or PC Magazine July 1992 (xi:13) page 496, for details. INT 21 AH=69 also gets and sets the volume label in the boot record, which is not necessarily the same as "the" volume label displayed by the DIR, VOL, and LABEL commands. For that volume label, see "412. How can I read, create, change, or delete the volume label?" Subject: 414. What's the format of .OBJ, .EXE., .COM files? Please see "206. What's the format of an .OBJ file?"; "207. What's the format of an .EXE header?"; and "208. What's the difference between .COM and .EXE formats?" Subject: 415. How can I flush the software disk cache? Please see "701. How can a program reboot my PC?" section 5. Serial ports (COM ports) =================================== Subject: 501. How do I set my machine up to use COM3 and COM4? Unless your machine is fairly old, it's probably already set up. After installing the board that contains the extra COM port(s), check the I/O addresses in word 0040:0004 or 0040:0006. (In DEBUG, type "D 40:4 L4" and remember that every word is displayed low byte first, so if you see "03 56" the word is 5603.) If those addresses are nonzero, your PC is ready to use the ports and you don't need the rest of this answer. If the I/O address words in the 0040 segment are zero after you've installed the I/O board, you need some code to store these values into the BIOS data segment: 0040:0004 word I/O address of COM3 0040:0006 word I/O address of COM4 0040:0011 byte (bits 3-1): number of serial ports installed The documentation with your I/O board should tell you the port addresses. When you know the proper port addresses, you can add code to your program to store them and the number of serial ports into the BIOS data area before you open communications. Or you can use DEBUG to create a little program to include in your AUTOEXEC.BAT file, using this script: n SET_ADDR.COM <--- or a different name ending in .COM a 100 mov AX,0040 mov DS,AX mov wo [0004],aaaa <--- replace aaaa with COM3 address or 0 mov wo [0006],ffff <--- replace ffff with COM4 address or 0 and by [0011],f1 or by [0011],8 <--- use number of serial ports times 2 mov AH,0 int 21 <--- this line must be blank rCX 1f rBX 0 w q Subject: 502. How do I find the I/O address of a COM port? (rev: 24 Mar 1994) Look in the four words beginning at 0040:0000 for COM1 through COM4. (The DEBUG command "D 40:0 L8" will do this. Remember that words are stored and displayed low byte first, so a word value of 03F8 will be displayed as F8 03.) If the value is zero, that COM port is not installed (or you've got an old BIOS; see "501. How do I set my machine up to use COM3 and COM4?"). If the value is nonzero, it is the I/O address of the transmit/receive register for the COM port. Each COM port occupies eight consecutive I/O addresses (though many chips use only the first seven). Here's some C code to find the I/O address: unsigned ptSel(unsigned comport) { unsigned io_addr; if (comport >= 1 && comport <= 4) { unsigned far *com_addr = (unsigned far *)0x00400000UL; io_addr = com_addr[comport-1]; } else io_addr = 0; return io_addr; } You might also want to explore Port Finder, downloadable as /pub/msdos/io_util/pf271.zip at SimTel /pub/msdos/utilities/sysutl/pf271.zip at nic.funet.fi I haven't tried it myself, but a posted article reviewed it very favorably and said it also lets you swap ports around. Subject: 503. But aren't the COM ports always at I/O addresses 3F8, 2F8, 3E8, and 2E8? The first two are usually right (though not always); the last two are different on many machines. Subject: 504. How do I configure a COM port and use it to transmit data? (rev: 17 Sep 1993) Do you want actual code, or do you want books that explain what's going on? 1) Source code First, check your compiler's run-time library. Many compilers offer functions similar to Microsoft C's _bios_serialcom() or Borland's bioscom(), which may meet your needs. Second, check for downloadable resources at SimTel and Garbo. At SimTel, /pub/msdos/c/pcl4c34.zip (March 1993) is described as "Asynchronous communications library for C"; Garbo has a whole /pc/comm directory. Also, an extended example is in Borland's TechFax TI445, downloadable as part of /pub/msdos/turbo-c/bchelp10.zip at SimTel /pc/turbopas/bchelp10.zip at Garbo. Though written by Borland, much of it is applicable to other forms of C, and it should give you ideas for other programming languages. 2) Reference books Highly recommended: Joe Campbell's {C Programmer's Guide to Serial Communications}, ISBN 0-672-22584-0. He gives complete details on how serial ports work, along with complete programs for doing polled or interrupt-driver I/O. The book is quite thick, and none of it looks like filler. If Campbell's book is overkill for you, you'll find a good short description of serial I/O in {DOS 5: A Developer's Guide}, ISBN 1-55851-177-6, by Al Williams. Finally, a reader has recommended {Serial Communications Programming in C/C++} by Mark Goodwin (ISBN 1558281983), with source code in the book and on disk. Topics include the basics, various methods of serial communications on the PC (with consideration of high-speed modems), ANSI screen interface, file transfer protocols (Xmodem and Ymodem), etc. There is code in C, and that code is extended into a C++ class for those who use C++. There are also subroutines in Assembly. 3) Downloadable information files A "Serial Port FAQ" is occasionally posted to this newsgroup, and is downloadable as multiple files: /pub/usenet/comp.os.msdos.programmer/T_S_P*_3 from rtfm.mit.edu /pub/E-Technik/afd/*Serial* from pfsparc02.phil15.uni-sb.de. For rtfm.mit.edu instructions, see "C06. Where are FAQ lists archived?" (The uni-sb.de archive administrator warns that the ftp address may change, sometime in the future, to etcip1.ee.uni-sb.de.) section 6. Other hardware questions and problems ================================================ Subject: 601. Which 80x86 CPU is running my program? (rev: 24 Mar 1994) According to an article posted by Michael Davidson, Intel's approved code for distinguishing among 8086, 80286, 80386, and 80486 and for detecting the presence of an 80287 or 80387 is published in Intel's 486SX processor manual (order number 240950-001). David Kirschbaum's improved version of this is downloadable as /pub/msdos/sysinfo/cpuid593.zip from SimTel /pc/sysinfo/cpuid593.zip from Garbo. According to an article posted by its author, WCPU knows the differences between DX and SX varieties of 386 and 486 chips, and can detect a math coprocessor and a Pentium. It's downloadable as /pub/msdos/sysinfo/wcpu050.zip at SimTel /pc/sysinfo/wcpu050.zip at Garbo. Subject: 602. How can a C program send control codes to my printer? If you just fprintf(stdprn, ...), C will translate some of your control codes. The way around this is to reopen the printer in binary mode: prn = fopen("PRN", "wb"); You must use a different file handle because stdprn isn't an lvalue. By the way, PRN or LPT1 must not be followed by a colon in DOS 5.0. There's one special case, Ctrl-Z (ASCII 26), the DOS end-of-file character. If you try to send an ASCII 26 to your printer, DOS simply ignores it. To get around this, you need to reset the printer from "cooked" to "raw" mode. Microsoft C users must use INT 21 AH=44, "get/set device information". Turbo C and Borland C++ users can use ioctl to accomplish the same thing: ioctl(fileno(prn), 1, ioctl(fileno(prn),0) & 0xFF | 0x20, 0); An alternative approach is simply to write the printer output into a disk file, then copy the file to the printer with the /B switch. A third approach is to bypass DOS functions entirely and use the BIOS printer functions at INT 17. If you also fprintf(stdprn,...) in the same program, you'll need to use fflush() to synchronize fprintf()'s buffered output with the BIOS's unbuffered. By the way, if you've opened the printer in binary mode from a C program, remember that outgoing \n won't be translated to carriage return/line feed. Depending on your printer, you may need to send explicit \n\r sequences. Subject: 603. How can I redirect printer output to a file? Please see "408. How can I redirect printer output to a file?" Subject: 604. Which video adapter is installed? The technique below should work if your BIOS is not too old. It uses three functions from INT 10, the BIOS video interrupt. (If you're using a Borland language, you may not have to do this the hard way. Look for a function called DetectGraph or something similar.) Set AX=1200, BL=32 and call INT 10. If AL returns 12, you have a VGA. If not, set AH=12, BL=10 and call INT 10 again. If BL returns 0,1,2,3, you have an EGA with 64,128,192,256K memory. If not, set AH=0F and call INT 10 a third time. If AL is 7, you have an MDA (original monochrome adapter) or Hercules; if not, you have a CGA. This worked when tested with a VGA, but I had no other adapter types to test it with. Subject: 605. How do I switch to 43- or 50-line mode? /pub/msdos/screen/vidmode.zip, downloadable from SimTel, contains .COM utilities and .ASM source code. Subject: 606. How can I find the Microsoft mouse position and button status? Use INT 33 AH=3, described in Ralf Brown's interrupt list (Q C03). The Windows manual says that the Logitech mouse is compatible with the Microsoft one, so the interrupt will probably work the same. Also, many files are downloadable from /pub/msdos/mouse/*.* at SimTel. Subject: 607. How can I access a specific address in the PC's memory? (rev: 6 Jun 1994) First check the library that came with your compiler. Many vendors have some variant of peek and poke functions. For example: - In Turbo Pascal, use the pseudo-arrays Mem, MemW, and MemL. Be sure you use the correct array for the size of data you want to access: byte, word, or double word. - In Turbo C/Borland C, and in recent versions of Microsoft C, use MK_FP; in older versions of Microsoft C, use FP_OFF and FP_SEG. (Caution: Turbo C and Turbo C++ also have FP_OFF and FP_SEG macros, but they can't be used to construct a pointer.) Be sure to pick the right data type: probably "unsigned char far *" if you're planning to access bytes and "unsigned short far *" for words. (The "far" isn't needed if your memory model uses 32-bit data pointers, but including it does no harm.) By the way, it's not useful to talk about "portable" ways to do this. Any operation that is tied to a specific memory address is not likely to work on another kind of machine. Subject: 608. How can I read or write my PC's CMOS memory? (rev: 24 Mar 1994) There are a great many public-domain utilities that do this. These are downloadable from SimTel in directory /pub/msdos/at: cmos14.zip 5965 920817 Saves/restores CMOS to/from file cmoser11.zip 28323 910721 386/286 enhanced CMOS setup program cmosram.zip 76096 920214 Save AT/386/486 CMOS data to file and restore rom2.zip 15692 900131 Save AT and 386 CMOS data to file and restore setup21.zip 18172 880613 Setup program which modifies CMOS RAM viewcmos.zip 11068 900225 Display contents of AT CMOS RAM, w/C source A program to check and display CMOS memory (but not write to it) is downloadable as part of /pc/ts/tsutle22.zip at Garbo /pub/msdos/sysutil/tsutle22.zip at SimTel. Good reports of CMOS299.ZIP, available in the pc.dir directory of cantva.canterbury.ac.nz [132.181.30.3], have been posted. Of the above, my only experience is with CMOSRAM, which seems to work fine. It contains an excellent (and witty) .DOC file that explains the hardware involved and gives specific recommendations for preventing disaster or recovering from it. It's $5 shareware. Robert Jourdain's {Programmer's Problem Solver for the IBM PC, XT, and AT} has code for accessing the CMOS RAM, according to an article posted in this newsgroup. Subject: 609. How can I access memory beyond 640K? (rev: 24 Mar 1994) PC Magazine 29 June 1993 (xii:12) pages 302-304 carry an article, "How DOS Programs Can Use Over 1MB of RAM". section 7. Other software questions and problems ================================================ Subject: 701. How can a program reboot my PC? (rev: 24 Mar 1994) You can generate a "cold" boot or a "warm" boot. A cold boot is the same as turning the power off and on; a warm boot is the same as Ctrl-Alt-Del and skips the power-on self 'test. For a warm boot, store the hex value 1234 in the word at 0040:0072. For a cold boot, store 0 in that word. Then, if you want to live dangerously, jump to address FFFF:0000. Here's C code to do it: /* WARNING: data loss possible */ void bootme(int want_warm) /* arg 0 = cold boot, 1 = warm */ { void (far* boot)(void) = (void (far*)(void))0xFFFF0000UL; unsigned far* type = (unsigned far*)0x00400072UL; *type = (want_warm ? 0x1234 : 0); (*boot)( ); } What's wrong with that method? It will boot right away, without closing files, flushing disk caches, etc. If you boot without flushing a write-behind disk cache (if one is running), you could lose data or trash the file allocation table in your hard drive. There are two methods of signaling the cache to flush its buffers: (1) simulate a keyboard Ctrl-Alt-Del in the keystroke translation function of the BIOS (INT 15 AH=4F; but see notes below), and (2) issue a disk reset (DOS function 0D). Most disk-cache programs hook one or both of those interrupts, so if you use both methods you'll probably be safe. When user code simulates a Ctrl-Alt-Del, one or more of the programs that have hooked INT 15 AH=4F can ask that the key be ignored by clearing the carry flag. For example, HyperDisk does this when it has started but not finished a cache flush. So if the carry flag comes back cleared, the boot code has to wait a couple of clock ticks and then try again. (None of this matters on older machines whose BIOS can't support 101- or 102-key keyboards; see the discussion of INT 21 AH=4F in "307. What is the SysRq key for?") C code that tries to signal the disk cache (if any) to flush is given below. Turbo Pascal code by Timo Salmi that does more or less the same job may be found at question 49 (as of this writing) in the Turbo Pascal FAQ in comp.lang.pascal, and is downloadable as file FAQPAS2.TXT, which is part of /pc/ts/tsfaqp18.zip at Garbo /pub/msdos/info/tsfaqp18.zip at SimTel. Here's C code that reboots after trying to signal the disk cache: #include void bootme(int want_warm) /* arg 0 = cold boot, 1 = warm */ { union REGS reg; void (far* boot)(void) = (void (far*)(void))0xFFFF0000UL; unsigned far* boottype = (unsigned far*)0x00400072UL; char far* shiftstate = (char far*)0x00400017UL; unsigned ticks; int time_to_waste; /* Simulate reception of Ctrl-Alt-Del: */ for (;;) { *shiftstate |= 0x0C; /* turn on Ctrl & Alt */ reg.h.ah = 0x4F; /* see notes below */ reg.h.al = 0x53; /* 0x53 = Del's scan code */ reg.x.cflag = 1; /* sentinel for ignoring key */ int86(0x15, ®, ®); /* If carry flag is still set, we've finished. */ if (reg.x.cflag) break; /* Else waste some time before trying again: */ reg.h.ah = 0; int86(0x1A, ®, ®);/* system time into CX:DX */ ticks = reg.x.dx; for (time_to_waste = 3; time_to_waste > 0; ) { reg.h.ah = 0; int86(0x1A, ®, ®); if (ticks != reg.x.dx) ticks = reg.x.dx , --time_to_waste; } } /* Issue a DOS disk reset request: */ reg.h.ah = 0x0D; int86(0x21, ®, ®); /* Set boot type and boot: */ *boottype = (want_warm ? 0x1234 : 0); (*boot)( ); } Reader Timo Salmi reported (26 July 1993) that the INT 15 AH=4F call may not work on older PCs (below AT, XT2, XT286), according to Ralf Brown's interrupt list (Q C03). Reader Roger Fulton reported (1 July 1993) that INT 15 AH=4F hangs even a modern PC "ONLY when ANSI.SYS [is] loaded high using EMM386.EXE. (Other things loaded high with EMM386.EXE were OK; ANSI.SYS loaded high with QEMM386.SYS was OK; ANSI.SYS loaded low with EMM386.EXE installed was OK.)" His solution was to use only the disk reset, INT 21 AH=0D, which does flush SMARTDRV, then wait five seconds in hopes that any other disk-caching software would have time to flush its queue. Reader Per Bergland reported (10 Sep 1993) that the jump to FFFF:0000 will not work in Windows or other protected-mode programs. (For example, when the above reboot code ran in a DOS session under Windows, a box with "waiting for system shutdown" appeared. The PC hung and had to be reset by cycling power.) His solution, which does a cold boot not a warm boot, is to pulse pin 0 of the 8042 keyboard controller, which is connected to the CPU's "reset" line. He has tested the following code on various Compaqs, and expects it will work for any AT-class machine; he cautions that you must first flush the disk cache as indicated above. cli @@WaitOutReady: ; Busy-wait until 8042 ready for new command in al,64h ; read 8042 status byte test al,00000010b ; this bit indicates input buffer full jnz @@WaitOutReady mov al,0FEh ; Pulse "reset" = 8042 pin 0 out 64h,al ; The PC will reboot now Subject: 702. How can I time events with finer resolution than the system clock's 55 ms (about 18 ticks a second)? (rev: 24 Mar 1994) The following files, among others, are downloadable from SimTel: /pub/msdos/at : atim.zip 4783 881126 Precision program timing for AT /pub/msdos/c : millisec.zip 37734 911205 MSC/asm src for millisecond timing mschrt3.zip 53708 910605 High-res timer toolbox for MSC 5.1 msec_12.zip 8484 920320 High-def timer v1.2 (C,ASM) ztimer11.zip 77625 920428 Microsecond timer for C, C++, ASM (also at Garbo as /pc/c/ztimer11.zip) /pub/msdos/turbo_c : tchrt3.zip 53436 910606 High-res timer for Turbo C 2.0 tctimer.zip 15609 891030 High-res timing for Turbo C (same as /pc/c/tctimer.zoo at Garbo; both are version 1.0) For Turbo Pascal users, source and object code are downloadable in /pub/msdos/turbopas/bonus507.zip at SimTel /pc/turbopas/bonus507.zip at Garbo. Also see "Q: How is millisecond timing done?" in FAQPAS.TXT, downloadable as part of /pc/ts/tsfaqp18.zip at Garbo /pub/msdos/info/tsfaqp18.zip at SimTel. Subject: 703. How can I find the error level of the previous program? (rev: 24 Mar 1994) First, which previous program are you talking about? If your current program ran another one, when the child program ends its error level is available to the program that spawned it. Most high- level languages provide a way to do this; for instance, in Turbo Pascal it's Lo(DosExitCode) and the high byte gives the way in which the child terminated. In Microsoft C, the exit code of a synchronous child process is the return value of the spawn-type function that creates the process. If your language doesn't have a function to return the error code of a child process, you can use INT 21 AH=4D (get return code). By the way, this will tell you the child's exit code and the manner of its ending (normal, Ctrl-C, critical error, or TSR). It's much trickier if the current program wants to get the error level of the program that ran and finished before this one started. G.A.Theall has published source and compiled code to do this; the code is downloadable as /pub/msdos/batutil/errlvl13.zip at SimTel /pc/batchutil/errlvl12.zip (an older version) at Garbo. (The code uses undocumented features in DOS 3.3 through 5.0. Theall says in the .DOC file that the values returned under 4DOS or other replacements won't be right.) Subject: 704. How can a program set DOS environment variables? (rev: 24 Mar 1994) Program functions that read or write "the environment" typically access only the program's copy of it. What this Q really wants to do is to modify the active environment, the one that is affected by SET commands in batch files or at the DOS prompt. You need to do some programming to find the active environment, and that depends on the version of DOS. A fairly well-written article in PC Magazine 28 Nov 1989 (viii:20), pages 309-314, explains how to find the active environment, and includes Pascal source code. The article hints at how to change the environment, and suggests creating paths longer than 128 characters as one application. Now as for downloadable source code, there are many possibilities. I looked at some of these, and liked /pub/msdos/envutil/rbsetnv1.zip at SimTel /pc/envutil/rbsetnv1.zip at Garbo the best. It includes some utilities to manipulate the environment, with source code in C. A newer program is /pub/msdos/batutil/strings2.zip at SimTel part of /pc/pcmag/vol11n22.zip at Garbo, which is the code from PC Magazine 22 Dec 1992 (xi:22). You can also use a call to INT 2E, Pass Command to Interpreter for Execution; see Ralf Brown's interrupt list (Q C03) for details and cautions. Subject: 705. How can I change the switch character to - from /? (rev: 20 Mar 1994) Under DOS 5.0 and above, you can't--not completely, anyway. INT 21 AX=3700, get switch character, always returns a '/' (hex 2F). But the DOS commands don't even call that function: they simply hard code '/' as the switch character. Some history: DOS used to let you change the switch character by using SWITCHAR= in CONFIG.SYS or by calling DOS function 3701. DOS commands and other programs called DOS function 3700 to find out the switch character. If you changed the switch character to '-' (the usual choice), you could then type "dir c:/c700 -p" rather than "dir c:\c700 /p". Under DOS 4.0, the DOS commands ignored the switch character but functions 3700 and 3701 still worked and could be used by other programs. Under DOS 5.0, even those functions no longer work, though all DOS functions still accept '/' or '\' in file specs. You can reactivate the functions to get and set switchar by using programs like SLASH.ZIP or the sample TSR called SWITCHAR in amisl091.zip (see "706. How can I write a TSR (terminate-stay- resident utility)?"). DOS commands will still use the slash, but non-DOS programs that call DOS function 3700 will use your desired switch character. (DOS replacements like 4DOS may honor the switch character for internal commands.) Some readers may wonder why this is even an issue. Making '-' the switch character frees up the front slash to separate names in the path part of a file spec. This is easier for the ten-fingered to type, and it's one less difference to remember for commuters between DOS and Unix. The switch character is the only issue, since all the INT 21 functions accept '/' or '\' to separate directory names. Subject: 706. How can I write a TSR (terminate-stay-resident utility)? (rev: 24 Mar 1994) There are books, and there's code to download. First, the books: - Ray Duncan's {Advanced MS-DOS}, ISBN 1-55615-157-8, gives a brief checklist intended for experienced programmers. The ISBN is for the second edition, through DOS 4; but check to see whether the DOS 6 version is available yet. - {DOS 5: A Developer's Guide} by Al Williams, ISBN 1-55851-177-6, goes into a little more detail, 90 pages worth! - Pascal programmers might look at {The Ultimate DOS Programmer's Manual} by John Mueller and Wallace Wang, ISBN 0-8306-3534-3, for an extended example in mixed Pascal and assembler. - For a pure assembler treatment, check Steven Holzner's {Advanced Assembly Language}, ISBN 0-13-663014-6. He has a book with the same title out from Brady Press, but it's about half as long as this one. Next, the code. Some of it is companion code to published articles, which are also listed below: - The Alternate Multiplex Interrupt Specification, downloadable as /pub/msdos/info/altmpx35.zip at SimTel /pc/programming/altmpx35.zip at Garbo /afs/cs/user/ralf/pub/altmpx35.zip at cs.cmu.edu - Ralf Brown's assembly-language implementation of the spec, with utilities in C, is downloadable as /pub/msdos/asmutil/amisl091.zip at SimTel /pc/c/amisl091.zip at Garbo /afs/cs/user/ralf/pub/amisl091.zip at cs.cmu.edu - Douglas Boling's MASM template for a TSR is downloadable as /pub/msdos/asmutl/template.zip at SimTel. - A posted article mentions Boling's "Strategies and Techniques for Writing State-of-the-Art TSRs that Exploit MS-DOS 5", Microsoft Systems Journal, Jan-Feb 1992, Volume 7, Number 1, pages 41-59, with examples downloadable in /pub/msdos/msjournal/msjv7-1.zip at SimTel - code for Al Stevens's "Writing Terminate-and-Stay-Resident Programs", Computer Language, February 1988, pages 37-48 and March 1988, pages 67-76 is downloadable as /pub/msdos/c/tsrc.zip at SimTel - software examples to accompany Kaare Christian's "Using Microsoft C Version 5.1 to Write Terminate-and-Stay-Resident Programs", Microsoft Systems Journal, September 1988, Volume 3, Number 5, pages 47-57 are downloadable as /pub/msdos/msjournal/msjv3-5.arc at SimTel Finally, there are commercial products, of which TesSeRact (for C- language TSRs) is one of the best known. Subject: 707. Why does my interrupt function behave strangely? (rev: 24 Sep 1993) Interrupt service routines can be tricky, because you have to do some things differently from "normal" programs. If you make a mistake, debugging is a pain because the symptoms may not point at what's wrong. Your machine may lock up or behave erratically, or just about anything else can happen. Here are some things to look for. (See "706. How can I write a TSR (terminate-stay-resident utility)?" for general techniques that may prevent a problem.) First, did you fail to set up the registers at the start of your routine? When your routine begins executing, you can count on having CS point to your code segment and SS:SP point to some valid stack (of unknown length), and that's it. In particular, an interrupt service routine must set DS to DGROUP before accessing any data in its data segments. (If you're writing in a high-level language, the compiler may generate this code for you automatically; check your compiler manual. For instance, in Borland and Microsoft C, give your function the "interrupt" attribute.) Did you remember to turn off stack checking when compiling your interrupt server and any functions it calls? The stack during the interrupt is not where the stack-checking code expects it to be. (Caution: Some third-party libraries have stack checking compiled in, so you can't call them from your interrupt service routine.) Next, are you calling any DOS functions (INT 21, 25, or 26) in your routine? DOS is not re-entrant. This means that if your interrupt happens to be triggered while the CPU is executing a DOS function, calling another DOS function will wreak havoc. (Some DOS functions are fully re-entrant, as noted in Ralf Brown's interrupt list (Q C03). Also, your program can test, in a way too complicated to present here, when it's safe to call non-re-entrant DOS functions. See INT 28, INT 21 AH=34, and INT 21 AX=5D06 or 5D0B; and consult {Undocumented DOS} by Andrew Schulman. Your program must read both the "InDOS flag" and the "critical error flag".) Is a function in your language library causing trouble? Does it depend on some initializations done at program startup that is no longer available when the interrupt executes? Does it call DOS (see preceding paragraph)? For example, in both Borland and Microsoft C the memory-allocation functions (malloc(), etc..) call DOS functions and also depend on setups that they can't get at from inside an interrupt; so do the standard I/O functions like scanf() and printf(). Many other library functions have the same problem, so you can't use them inside an interrupt function without special precautions. Is your routine simply taking too long? This can be a problem if you're hooking on to the timer interrupt, INT 1C or INT 8. That interrupt expects to be called about every 55 ms, which is 18.2 times a second. Therefore your routine, plus any others hooked to the same interrupts, must execute in less than 55 ms. If they use even a substantial fraction of that time, you'll see significant slowdowns of your foreground program. A good discussion is downloadable as pub/msdos/SIMTEL20-mirror/info/intshare.zip at ni.funet.fi /pub/msdos/info/intshare.zip at SimTel. Did you forget to restore all registers at the end of your routine? Did you chain improperly to the original interrupt? You need to restore the stack to the way it was upon entry to your routine, then do a far jump (not call) to the original interrupt service routine. (The process is a little different in high-level languages.) Subject: 708. How can I write a device driver? Many books answer this in detail. Among them are {Advanced MS-DOS} and {DOS 5: A Developer's Guide}, cited in the preceding Q. Michael Tischer's {PC System Programming}, ISBN 1-55755-036-0, has an extensive treatment, as does Dettman and Kyle's {DOS Programmer's Reference: 2d Edition}, ISBN 0-88022-458-4. For a really in-depth treatment, look for a specialized book like Robert Lai's {Writing MS- DOS Device Drivers}, ISBN 0-201-13185-4. Subject: 709. What can I use to manage versions of software? (rev: 21 Aug 1993) A port of the Unix RCS utility is downloadable as /pub/msdos/gnuish/rcs55ax.zip (EXE and docs) from SimTel /pub/msdos/gnuish/rcs55as.zip (source) from SimTel /pc/unix/alrcs5ex.zip (EXE and docs ?) from Garbo. This version of RCS is no longer limited to one-character extensions on filenames (for example, .CPP and .BAS are now OK). An RCS56 is available at a number of archive sites, but it appears to be unauthorized. In response to a query, Keith Petersen, SimTel administrator, said that RCS56 was removed from SimTel at the author's request because it did not contain source code and thus was in violation of the GNU copyleft. As for commercial software, I posted a question asking for readers' experiences in July 1993 and seven readers responded. PVCS from Intersolv (formerly Polymake) got five positive reviews, though several readers commented that it's expensive; RCS from MKS got one positive and one negative review; Burton TLIB got one negative review; DRTS from ILSI got one positive review. Subject: 710. What's this "null pointer assignment" after my C program executes? (rev: 20 Mar 1994) Somewhere in your program, you assigned a value _through_ a pointer without first assigning a value _to_ the pointer. (This might have been something like a strcpy() or memcpy() with a pointer as its first argument, not necessarily an actual assignment statement.) Your program may look like it ran correctly, but if you get this message you can be certain that there's a bug somewhere. Microsoft and Borland C, as part of their exit code (after a call to exit() or a return from your main function), check whether the location 0000 in your data segment contains a different value from what you started with. If so, they infer that you must have used an uninitialized pointer. This implies that the message will appear at the end of execution of your program regardless of where the error actually occurred. To track down the problem, you can put exit() calls at various spots in the program and narrow down where the uninitialized pointer is being used by seeing which added exit() makes the null-pointer message disappear. Or, if your program was compiled with small or medium models, which use 16-bit data pointers, tell the debugger to set a watch at location 0000 in your data segment. (If data pointers are 32 bits, as in the compact and large models, a null pointer will overwrite the interrupt vectors at 0000:0000 and probably lock up your machine.) Under MSC/C++ 7.0, you can declare the undocumented library function extern _cdecl _nullcheck(void); and then sprinkle calls to _nullcheck() through your program at regular intervals. Borland's TechFax document TI726 discusses the null pointer assignment from a Borland point of view. It's one of many documents downloadable as part of /pub/msdos/turbo-c/bchelp10.zip at SimTel /pc/turbopas/bchelp10.zip at Garbo. Subject: 711. How can a batch file tell whether it's being run in a DOS box under Windows? (new: 20 Mar 1994) When Windows 3.0 or 3.1 is running, the DOS environment will contain a definition of the string windir, in lower case. That's not really useful, however, because the batch statement if "%windir%" == "" ... will test for an environment variable WINDIR in upper case. Your only real option is to write a program as suggested by the following Q, and have it return a value which your batch file can test via "if errorlevel". Subject: 712. How can my program tell if it's running under Windows? (rev: 20 Mar 1994) Execute INT 2F AX=4680. If AX returns 0, you're in Windows real mode or standard mode (or under the DOS shell). Otherwise, call INT 2F AX=1600. If AL returns something other than 0 or 80, you're in Windows 386 enhanced mode. See PC Magazine 24 Nov 1992 (xi:20) pages 492-493. For more information, see PC Magazine 26 May 1992 (xi:10) pages 345- 346. A program, WINMODE, is available as part of /pub/msdos/pcmag/vol11n10.zip at SimTel /pc/pcmag/vol11n10.zip at Garbo. PC Magazine 29 March 1994 (xiii:6) pages 312 and 320 published a new program, WINVER. This would be in /pub/msdos/pcmag/vol13n06.zip at SimTel /pc/pcmag/vol13n06.zip at Garbo. Subject: 713. How can a program tell whether ANSI.SYS is installed? (new: 20 Apr 1994) In DOS 4.0 and above, call INT 2F AX=1A00. If the value FF is returned in AL, ANSI.SYS is installed. For more information, see Ralf Brown's interrupt list (question C03). Subject: 799. How do I copyright software that I write? (rev: 9 Sep 1993) You can download a very comprehensive answer from the Internet. Terry Carroll posts a six-part Copyright FAQ to misc.legal, news.answers and other groups. A short answer follows, not based on that article. Disclaimer: I am not a lawyer, and this is not legal advice. Also, there are very likely to be differences in copyright law among nations. No matter where you live, if significant money may be involved, get legal advice. The following is adapted (and greatly condensed) from chapter 4 of the Chicago Manual of Style (13th edition, ISBN 0-226-10390-0). In the U.S. (at least), when you write something, you own the copyright. (The exception that matters most to programmers is "works made for hire", i.e., code you write because your employer or client pays you to. A contract, agreed in advance, can vest the copyright in the programmer even if an employee; otherwise the employer owns the copyright.) You don't have to register the work with the Copyright Office unless (until) the copyright is infringed and you intend to bring suit; however, it is easier to recover damages in court if you did register the work within three months of publication. From paragraph 4.16 of the Chicago Manual: "... the [copyright] notice consists of three parts: (1) the symbol [C-in-a-circle] (preferred because it also suits the requirements of the Universal Copyright Convention), the word 'Copyright', or the abbreviation 'Copr.', (2) the year of first publication, and (3) the name of the copyright owner. Most publishers also add the phrase 'All rights reserved' because it affords some protection in Central and South American countries ...." Surprise: "(C)" is legally not the same as the C-in-a-circle, so those of us who are ASCII-bound must use the word or the abbreviation. section A. Downloading ====================== Subject: A01. What are SimTel, Garbo, and wustl? (rev: 6 Apr 1994) These are three of the most popular archive sites, with a few bazillion files available for free downloading by ftp. (For email access, see "A02. I have no ftp access. How can I get files from the archives?".) Many of the files are shareware and you're expected to send a payment directly to the authors if you use them regularly. In comp.archives.msdos.d, Samuel Ko posts a two-part "Useful MS-DOS Programs at SIMTEL20 and Garbo"; it's downloadable as /pub/msdos/info/useful34.zip at SimTel /pc/filelist/useful34.zip at Garbo /pub/usenet/news.answers/msdos-archives/part* at rtfm.mit.edu. For rtfm.mit.edu instructions, see "C06. Where are FAQ lists archived?" A few words about file names and versions: Many files at the archive sites are updated from time to time. I verified every filename in this FAQ as of 24 Mar 1994 by ftp to the named sites, or by consulting their index files. If you can't find a file given in these articles as mumble12.zip, perhaps there's a newer version; try mumble13.zip or mumble14.zip, or mumble*.zip if your ftp program supports wildcards (most do so). Please let me know of any out-of- date file names. This FAQ should show both Garbo and SimTel directory and file names, if available, for every file mentioned for downloading. If you see a listing for only one of them, it means that the file was not found at the other site, or that the other site's catalog shows an old version. Also remember that caps and lower case filenames are not interchangeable at most archive sites. 1) SimTel = oak.oakland.edu is located at the University of Rochester in the USA, and there are also many mirror sites including wuarchive.wustl.edu, archive.orts.edu, ftp.uu.net, nic.funet.fi, archie.au, and nctucca.edu.tw. For instructions, see these monthly articles in comp.archives.msdos.announce: How to find files in the SIMTEL20 msdos collection How to order SIMTEL20 files via e-mail How to upload files to SIMTEL20 These are downloadable from SimTel as /pub/msdos/filedocs/aaaread.me /pub/msdos/filedocs/mailserv.inf /pub/msdos/filedocs/upload.inf. 2) Garbo = garbo.uwasa.fi [128.214.87.1] is located at the University of Vaasa in Finland and maintained by Timo Salmi (ts@uwasa.fi) and others. Garbo and SimTel contain many of the same files, but there are many differences too. Among them: the directory structures differ greatly, and case is significant in directory and file names at Garbo. 3) wustl = wuarchive.wustl.edu [128.252.135.4] mirrors, among others, Garbo (in /systems/ibmpc/garbo) and SimTel (in /systems/ibmpc/msdos). As with any mirror site, it may lag by a day or two, so you may not want to try it on the same day you see an upload notice posted. 4) others: A comprehensive list of MS-DOS archive sites is downloadable as /pc/pd2/moder35.zip at Garbo /pub/msdos/info/moder35.zip at SimTel. For archie.au via Telnet (different from the Archie file-finding mail servers): Oceanian users should try archie.au first. Paul Brooks has written to say that it "mirrors Garbo and SimTel-20 (in /micros/pc/simtel-20, /micros/pc/garbo) as well as many other archives. Telnetting to 'archie.au' and logging on as 'archie' (no password) will access the Oceanic ARCHIE server." Email Craig Warren (ccw@archie.au) for instructions if needed. Subject: A02. I have no ftp access. How can I get files from the archives? (rev: 14 June 1993) First, be sure that you have no ftp access before trying email methods. (Ask your sysadmin, or a knowledgeable user at your site.) ftp is better for you because it's faster, and it uses less net resources too. When using an email server, make sure the Reply-to path in your message is valid. If it's not, you'll get no reply from the server. Do wait a few days before assuming you're not going to get a response; some servers have long pending queues. After a suitable wait, get your sysadmin's help to correct your reply-to, and send your message again. Occasionally a machine goes down for an extended period, which may prevent a timely reply to your message. If you're sure your message bears a good reply path and you haven't got a reply in a week or so, you might send your message again, once. Don't post it as an article in a newsgroup. For files from SimTel, see "How to order SIMTEL20 files via e-mail", posted monthly in comp.archives.msdos.announce; or send email containing only the word "help" to listserv@vm1.nodak.edu. For instructions on using Garbo's email server, send a request to Timo Salmi at ts@uwasa.fi. The DEC Western Research Labs server will get files from any ftp site by ftp and then email them to you. Send email containing "help" to ftpmail@decwrl.dec.com. Subject: A03. Can I get archives on CD-ROM? (rev: 24 May 1993) Copies of the SimTel MS-DOS, Macintosh and Unix-C collections (also of wuarchive, cica, and others) are available from Walnut Creek CDROM, 1547 Palos Verdes, Suite 260, Walnut Creek, CA 94596-2228, telephone (800) 786-9907 or +1 510 674-0783, or FAX +1 510 674-0821, or email rab@cdrom.com. For a catalog of disks available, send email to info@cdrom.com, or ftp the catalog as /cdrom/catalog from cdrom.com. Subject: A04. Where do I find program ? (rev: 7 Aug 1993) You _are_ asking about shareware, freeware, or public-domain programs, right? Commercial software is not legally distributed through the net, in general. (Occasionally vendors will make patches available, but these are useful only to upgrade software you already own.) That said, there are several newsgroups to help you find a program. comp.binaries.ibm.pc.wanted is generally the best place to ask your question. Please review the guidelines in "108. What other technical newsgroups should I know about?" Download and check the indexes from SimTel and Garbo (see "A05. How can I check SimTel or Garbo before I post a request for a program?"). Unless what you're looking for is commercial software, there's a good chance it will be at one or both of those sites. The Archie servers maintain directories of many (not all) ftp sites worldwide. You can Telnet to a server or client to search for files, or perform a search by email. Subject: A05. How can I check SimTel or Garbo before I post a request for a program? (rev: 24 Mar 1994) SimTel and Garbo have indexes of their contents, which you can download and then search off line. Garbo's index file, /pc/INDEX.ZIP, contains an annotated list, often updated, of the MS-DOS files there. The news file /pc/pd2/news-pd2 contains selected news on all MS-DOS directories at Garbo. SimTel's index files, in /pub/msdos/filedocs, are updated several times a month. simlist.zip contains a list in text format. But you may prefer the file simindex.zip, which is comma-delimited for easy use with any of these search facilities: - Two downloadable search programs are simtel35.zip and simdir22.zip. - dBASE III or IV users can load the index from simindex.zip using instructions in simibm.inf and simibm.db3. - PC-FILE users should get simibm.hdr, which tells how to use simibm.ibm. Subject: A06. How do I download and decode a program I found? (rev: 7 Aug 1993) See the "Starter kit" and "Beginner's guide to binaries" in comp.binaries.ibm.pc, usually posted on the first and 15th of every month. Please wait for these articles to come around; don't post a request. If you can't wait, they are downloadable from Garbo as /pc/doc-net/starter.kit and bin.man rtfm.mit.edu in /pub/usenet/comp.binaries.ibm.pc . The file names are quite long; try look for names of the form *starter.kit* and *bin.man* For rtfm.mit.edu instructions, see "C06. Where are FAQ lists archived?" Most binaries are posted and sent through email in 'uuencode' format. The starter kit contains a uudecode program to turn this file back into binary. Since the uuencoded file is bigger than the binary, you'll save connect time if you can uudecode it and then download the binary file. Remember to set file type to binary. Subject: A07. Where is UUDECODE? You can find it at SimTel and Garbo, but it's easier to take it from the "starter kit" mentioned in the preceding Q. If you're logged in at a Unix site, there's almost certainly a uudecode there: just type "uudecode" followed by a space and the file name. The binary file is 25% smaller than the uuencoded file, so you'll save connect time if you can uudecode it on the Unix host and then download the binary file. Remember: set file type binary. Subject: A08. Why do I get errors when extracting from a ZIP file I downloaded? (rev: 20 Mar 1994) There are many possible causes, but two of them probably account for 95% of all problems. 1) File transmission: You must tell the archive site to transfer ZIP files in binary mode. Depending on your software, you may also need to set your local software to receive files in binary mode. 2) Unzipping program: Make sure you aren't using an obsolete version. In <9303290853.kp28285@tacom-emh1.army.mil> on 29 Mar 1993, Keith Petersen, SimTel administrator, wrote: "SIMTEL20 has standardized on the Info-ZIP group's ZIP and UNZIP because they are freely distributable and they have no restrictions on exporting. The latest version of Info-ZIP's ZIP and UNZIP can always be found in directory" /pub/msdos/zip "and will always have the name 'Info- ZIP' in the description to make them easy to locate." PKUNZIP version 1.10 may not unzip newer stuff from archive sites because site administrators have now embraced version 2.04. Also see "B03. What's the current version of UNZIP?" section B. Vendors and products =============================== Subject: B01. How can I contact Borland? (rev: 6 Sep 1993) Borland has set up these email addresses. However, none of them is for technical support such as help with finding your own programming errors and explaining compiler messages. - bp7-info@borland.com will reply to any message with 17K of info on Borland Pascal with Objects 7.0 and Turbo Pascal 7.0. - customer-support@borland.com is for questions about prices and features of products, replacing bad or missing disks, info on upgrades, etc. They do not accept emailed credit-card numbers. - bugs@borland.com will take "a well-documented bug report" and send an automated response, but will not give you a workaround or a scheduled fix date or even confirm that it is or is not considered a bug. "The purpose of bugs@borland.com is to improve future products sooner, not as a substitute for tech support channels." Email tech support is available only through Compuserve (GO BOR). Telephone support is provided through separate phone numbers for most products. If you're calling from the U.S., dial (800) 841-8180 for a recorded list of toll numbers to call. Borland's BBS is at +1 408 439 9096. The surface-mail address is Technical Support Department, Borland International, P.O. Box 660001, Scotts Valley CA 95067-0001, USA. You'll need to give your product's name, version, and serial number. Patches for Borland products are archived at ftp.cica.indiana.edu in directory /pub/pc/borland . (I haven't verified this personally.) Borland's TechFax documents are also available for download: /pub/msdos/turbo-c/bchelp10.zip at SimTel /pc/turbopas/bchelp10.zip at Garbo. These documents are detailed answers to common questions about Turbo C and Borland C products, and aggregate several hundred Kbytes. Subject: B02. How can I contact Microsoft? (rev: 18 Sep 1993) Individual employees of Microsoft (not MicroSoft, please!) post here sometimes. Their addresses all take the form person@microsoft.com. However, Microsoft as a company does not answer individual questions via email through the Internet. 1) information available via anonymous ftp The company maintains an anonymous FTP server, ftp.microsoft.com. Effective 1 Oct 1993 the server will support "Microsoft development tools and advanced systems products, including Windows NT, the Win32 SDX, the Windows 3.1 SDK, Visual C++, Visual Basic, LAN Manager, SQL Server, and others," according to {Microsoft Developer News} for September 1993. The server contains "the complete Developer Knowledge Base with articles written and used by Microsoft Support Engineers. You will also find device drivers, patches, code samples, help files, and white papers." Readme files will "give an overview of the directory structure," which appears to be different from what was put in place in July 1993. For further information, says Microsoft, call (800) 936-5300. "Microsoft Developer Network technical articles and selected sample code files are available ... at ftp.uu.net ... in the subdirectory ~ftp/vendor/microsoft/developer-network" according to {Microsoft Developer News} for September 1993. 2) information via U.S. Mail Microsoft Product Support is at 16011 NE 36th Way, Box 97017, Redmond WA 98073-9717, USA. You can subscribe to the {Microsoft Developer News} by mailing a request to Microsoft Developer Network, P.O. Box 51812, Boulder CO 80322-1812, U.S.A. The nearest I can figure, this is free; certainly I've never paid for it or been asked to. 3) tech support via modem On Compuserve, GO MICROSOFT; or call Microsoft's BBS at +1 206 936- 6735 in the U.S., or +1 416 507-3022 in Canada. 4) tech support via voice telephone lines If you want to place an order or get general pre-sales information, call the appropriate sales and service number: U.S. end-user sales (800) 426-9400 U.S. corporate/gov't/reseller/ educational sales (800) 227-4679 Canadian sales (800) 568-3503 International sales +1 206 936-8661 For tech support you must make an ordinary long-distance phone call. Microsoft has separate incoming phone numbers for many products. Since it's your nickel, first check your documentation to see if a phone number is listed. Here are phone numbers (as of 1 June 1992) for a few products of most interest to the readers of this group: C/C++ (206) 635-7007 MASM (206) 646-5109 DOS Upgrade Users (206) 646-5104 (for 90 days after first call) Windows Users (206) 637-6098 If you can't find the direct number any other way, call the "master" numbers below or the sales numbers a few paragraphs above. You'll get the "voice mail phone tree from h-ll" but you'll eventually get to the right department. They don't provide technical assistance, but a voice menu will help you find the current phone number for the department you need. U.S. end-user product support (206) 454-2030 U.S. languages support (206) 637-7096 Subject: B03. What's the current version of UNZIP? (rev: 17 Mar 1994) Since April 1993, the administrators of Garbo and SimTel have accepted uploads in the ZIP 2.0 format. You can use the free Info- ZIP versions, or PKZIP 2.04g (not 2.04c or 2.04e). SimTel has standardized on the Info-ZIP versions for several reasons, as explained in an article posted 29 Mar 1993 in comp.archives.msdos.announce. Info-ZIP versions ZIP 2.0 and UNZIP 5.1 are now current. Those programs, ZIP 1.9, UNZIP 5.0, and PKZIP 2.04g all work with the same file formats. The primary source of the free Info-ZIP programs is at ftp.uu.net, directory /pub/archiving/zip; or at quest.jpl.nasa.gov, directory /pub. Files are in those directories or in subdirectories as shown below. The DOS executable for UNZIP is self extracting; all others require UNZIP 5.0 or 5.1: MSDOS/unzip51x.exe - DOS executable and doc, UNZIP 5.1 unzip51.zip - source code for UNZIP 5.1, all platforms MSDOS/zip20x.zip - DOS exe and doc, ZIP without crypt support zip201.zip - source code for ZIP 2.0, all platforms MSDOS/zcryp20x.zip - DOS exe and doc, ZIP with crypt support zcrypt21.zip - source code for ZIP crypt support WINDOWS/wunz20x.zip - Windows 3.1 WIZUNZIP 2.0 exe and help file WINDOWS/wunz20sr.zip - Windows 3.1 WIZUNZIP 2.0 source The essential files are also available at SimTel in /pub/msdos/zip and at Garbo in /pc/arcers. PKZIP and PKUNZIP are shareware products of PKWARE Inc. The current version is 2.04g, which is the third official version after 1.10. They are downloadable from PKWARE's bulletin board, +1 414 354 8670, or from Garbo as /pc/arcers/pkz204g.exe from SimTel as /pub/msdos/zip/pkz204g.exe By the way, if you want to develop your own utilities, you will find the ZIP 2.0 data structures described in the downloadable file /pub/msdos/zip/appnote.zip at SimTel. Subject: B04. What is the phone number for a vendor's BBS? (rev: 24 Mar 1994) Robert Baker (rbakerpc@delphi.com) uploaded a list of 800 bulletin- board support numbers operated by software vendors as of August 1993. It is downloadable as /pub/msdos/bbslist/bbs_9308.zip from SimTel. section C. More information =========================== Subject: C01. Are there any good on-line references for PC hardware components? (rev: 28 July 1993) Good reports of HELPPC21 have been posted. It is downloadable as /pub/msdos/info/helppc21.zip at SimTel /pc/programming/helppc21.zip at Garbo. This hypertext system contains much information on ports and other hardware, as well as some overlap with Ralf Brown's interrupt list (Q C03). It is shareware ($25). Subject: C02. Are there any good on-line references for PC interrupts? The definitive work is Ralf Brown's interrupt list; see Q C03. Subject: C03. What and where is "Ralf Brown's interrupt list"? (rev: 6 Jun 1994) This is megabytes of information on documented and (officially) undocumented BIOS and DOS interrupts, DOS tables, and interrupts hooked by many software packages. The interrupt list comes from cs.cmu.edu [128.2.222.173] in /afs/cs/user/ralf/pub (switch there with a single command) as inter41a.zip, inter41b.zip, and inter41c.zip; the separate file inter41d.zip contains utilities. The list is also downloadable as /pub/msdos/info/inter41.zip from SimTel /pc/programming/inter41.zip from Garbo. These versions were uploaded in early June 1994; updates are announced every few months in comp.archives.msdos.announce. Subject: C04. Where can I find lex, yacc, and language grammars? The FAQ list of the comp.compilers newsgroup answers this for Basic, C, Pascal, and other languages. See "C06. Where are FAQ lists archived?" Subject: C05. What's the best book to learn programming? Sorry, this FAQ list cannot settle religious arguments. Much of the heat over this topic arises because each person believes that the book that he or she learned from is the best book. But different people have very different experiences of the same book. The only person who can tell you which is the best book for learning a given topic is you. Your best bet is to go to a fairly well-stocked bookstore when you have a couple of hours to spare. Start at one end of the shelf and work your way methodically through every book that looks like it might cover what you want to learn. Look at the tables of contents; read a page or two from each book. Then make your decision. If money is a problem, or if you're not sure of your choice, check out your top two or three from your library. Subject: C06. Where are FAQ lists archived? (rev: 29 Mar 1994) Very possibly the FAQ list you want is already at your site. Check the newsgroup news.answers; if your site doesn't carry news.answers, check comp.answers, rec.answers, etc., according to the top-level name in the FAQ list's "home" newsgroup. Articles are posted to the *.answers groups in a way that should make them last until the next versions are posted. If they expire sooner at your site, you might want to lobby your sysadmin to treat the moderated *.answers groups as a special case and grant them longer expiration times than other groups. To ftp most FAQ lists, connect to rtfm.mit.edu, and change to directory /pub/usenet/news.answers. The name of the file that you want is the Archive-name from the top of the article. For instance, if the Archive-name is software-eng/part1 you would retrieve /pub/usenet/news.answers/software-eng/part1. By email (only if you have no ftp access, please), the server is mail-server@rtfm.mit.edu . It accepts "send" commands that omit the leading "/pub/" from file names; for example: send usenet/news.answers/software-eng/part1 For full instructions about the mail server, send it a message consisting of these two lines: help index Not just FAQ lists, but every article listed in the "List of Periodic Informational Postings" (LoPIP) can be obtained by ftp or email from rtfm.mit.edu. If you have an old copy of an informational article, look for an "Archive-name" at the beginning; rtfm.mit.edu stores it under that name in /pub/usenet/news.answers. If the article has no Archive-name, check the first name on the Newsgroups line and change to that directory under /pub/usenet. Or send email >>> with valid reply-to address << to brown@ncoast.org and you'll receive my canned instructions (about 8K) for retrieving FAQ lists for most newsgroups, including a few that aren't archived at rtfm.mit.edu. (This offer may be withdrawn without notice depending on system constraints.) Subject: C07. Where can I get the latest copy of this FAQ list? (rev: 30 Mar 1994) You can retrieve the latest version of this list as /pub/msdos/info/faqp*.zip from SimTel /pc/doc-net/faqp*.zip from Garbo. Check the date before downloading, to make sure that the archived version is actually newer than what you have. Like most FAQ lists, this one is archived at rtfm.mit.edu and a number of mirror sites. If you have ftp access, retrieve either of these identical files: /pub/usenet/news.answers/msdos-programmer-faq/faq /pub/usenet/comp.os.msdos.programmer/dos-faq If you have no ftp access, see "C06. Where are FAQ lists archived?" for instructions on retrieving it by email. Subject: C08. How do I use ftp? (rev: 6 Apr 1994) I was much impressed with {The Whole Internet User's Guide and Catalog} by Ed Krol (O'Reilly & Associates, second edition ISBN 1-56592-063-5). It gives lots of information on using ftp, email, Telnet, Archie, etc. As a new user of ftp (January 1993), I found the information made me productive quickly. (Disclosure: Though I don't believe it has biased my judgment, you should know that O'Reilly sent me a free evaluation copy.) You may also want to look for the "Beginner's Guide to FTP", posted periodically in comp.binaries.ibm.pc. You can retrieve it from rtfm.mit.edu (see "C06. Where are FAQ lists archived?"), in /pub/usenet/comp.binaries.ibm.pc, as *ftp.man*. When downloading a file by ftp, make sure you have write access to your working directory on your local machine, and that your disk has enough space to hold the files. Also make sure that if it's a ZIP file or other binary file type, you set the protocol to binary before downloading the file. (end of comp.os.msdos.programmer FAQ) -- Stan Brown, Oak Road Systems brown@Ncoast.ORG Can't find FAQ lists? ftp to 'rtfm.mit.edu' and look in /pub/usenet (or email me >>> with valid reply-to address <<< for instructions). I can also send "newbie" information on Usenet--just ask if you want it.