debug (command)

{{Infobox software

| name = DEBUG.COM (MS-DOS <= 2.0), DEBUG.EXE (MS-DOS >= 3.x)

| screenshot = File:Dosbox 001.png

| author = Tim Paterson

| developer = Microsoft, IBM, Digital Research, Novell, Caldera

| programming language = MS-DOS: x86 assembly language

| operating system = DOS, OS/2, Windows

| genre = Debugger

| license = MS-DOS v2.0, FreeDOS: MIT
OS/2, Windows: Proprietary software

| website = {{URL|https://technet.microsoft.com/en-us/library/bb491040.aspx|Debug}}

}}

The line-oriented debugger DEBUG.EXE is an external command in operating systems such as DOS, OS/2 and Windows (only in 16-bit/32-bit versions).

DEBUG can act as an assembler, disassembler, or hex dump program allowing users to interactively examine memory contents (in assembly language, hexadecimal or ASCII), make changes, and selectively execute COM, EXE and other file types. It also has several subcommands which are used to access specific disk sectors, I/O ports and memory addresses.

Overview

File:IBM PC DOS 1.0 screenshot.png 1.0.]]

File:Microsoft Windows 95 Version 4.00.1111 debug command 492x259.png DEBUG.EXE command]]

Traditionally, all computers and operating systems have included a maintenance function, used to determine whether a program is working correctly.{{Citation needed|date=June 2007}} DEBUG was originally written by Tim Paterson to serve this purpose in 86-DOS. When Paterson began working for Microsoft in the early 1980s he brought the program with him. DEBUG was part of {{nowrap|DOS 1.00}} and has been included in MS-DOS/PC DOS and certain versions of Microsoft Windows. Originally named DEBUG.COM, the executable was renamed into DEBUG.EXE with MS-DOS 3.2.

Windows XP and later versions included DEBUG for the MS-DOS subsystem to maintain MS-DOS compatibility. The 16-bit DOS commands are not available on 64-bit editions of Windows.

The MS-DOS/PC DOS DEBUG has several limitations:

In assembly/disassembly modes it only supports 8086 opcodes.
It can only access 16-bit registers and not 32-bit extended registers.
When the "N" subcommand for naming files is used, the filename is stored from offset DS:5D to DS:67 (the Program Segment Prefix File Control Block area), meaning that the program can only save files in FAT 8.3 filename format.

Enhanced DEBUG packages include the DEBUG command in Novell DOS 7, OpenDOS 7.01 and DR-DOS 7.02 and higher, a reimplementation of Digital Research's former Symbolic Instruction Debugger SID/SID86, which came with former versions of DR DOS. It is fully compatible with the DEBUG command line syntax of MS-DOS/PC DOS, but offers many enhancements, including supporting 16-bit and 32-bit opcodes up to the Pentium, an extended mode (/X) with dozens of additional commands and sub-modes, a much enhanced command line syntax with user-definable macros and symbolic debugging facilities with named registers, loaded symbol tables, mathematical operations and base conversions, as well as a commenting disassembler. Some versions also utilized DPMS to function as a "stealth mode" protected-mode debugger.

The FreeDOS version of DEBUG was developed by Paul Vojta and is licensed under the MIT License.

A 32-bit clone "DEBUGX" version supporting 32-bit DPMI programs exists as well. Andreas "Japheth" Grech, the author of the HX DOS extender, developed enhanced DEBUG versions 0.98 to 1.25, and former PC DOS developer Vernon C. Brooks added versions 1.26 to 1.32.

Syntax

DEBUG drive:][path] filename [parameters

When DEBUG is started without any parameters the DEBUG prompt, a "-" appears. The user can then enter one of several one or two-letter subcommands, including "A" to enter the assembler mode, "D" to perform a hexadecimal dump, "T" to trace and "U" to unassemble (disassemble) a program in memory.

DEBUG can also be used as a "DEBUG script" interpreter using the following syntax.

DEBUG < filename

A script file may contain DEBUG subcommands and assembly language instructions. This method can be used to create or edit binary files from batch files.

Using for non-debugging purposes

The DEBUG utility is useful for editing binary files in an environment where only DOS is installed without anything else. It can also be used to edit disk sectors, which is one method of removing boot-sector viruses.

Availability

Although technical documentation for the DEBUG command was removed with the release of MS-DOS 3.3, the command was retained in the standard distribution, unlike what was done with EXE2BIN.

Other operating systems

The operating systems Intel ISIS-II and iRMX 86, DEC TOPS-10 and TOPS-20, THEOS/OASIS, Zilog Z80-RIO, Stratus OpenVOS, PC-MOS, and AROS also provide a DEBUG command.

References

{{Reflist|refs=

{{cite web |author-first=Daniel B. |author-last=Sedory |title=A Guide to DEBUG |access-date=2014-11-29 |url=http://thestarman.pcministry.com/asm/debug/debug.htm}}

According to [http://msdn.microsoft.com/en-us/library/hb5z4sxd.aspx Microsoft Macro Assembler Reference], inline assembly is not supported for x64.

[https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb490895(v%3dtechnet.10) MS-DOS subsystem commands]

{{cite web |title=Microsoft TechNet Debug article |url=https://technet.microsoft.com/en-us/library/bb491040.aspx |access-date=2008-04-23}}

{{cite book |author-first=Günter |author-last=Born |author-link=:de:Günter Born |title=DOS 6 Tuning |language=de |publisher=Markt & Technik |date=1993 |edition=1 |isbn=3-87791-495-0}} (NB. Has several pages on MS-DOS DEBUG.EXE as well as on the Symbolic Instruction Debugger SID.EXE in DR DOS 5.0/6.0.)

{{cite book |title=DRDOSTIP.TXT — Tips und Tricks für DR DOS 3.41 - 5.0 |work=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=1997-05-24 |orig-date=1991 |edition=47 |language=de |url=http://www.antonis.de/dos/dos-tuts/mpdostip/html/drdostip.htm |access-date=2016-11-07 |url-status=live |archive-url=https://web.archive.org/web/20161107125452/http://www.antonis.de/dos/dos-tuts/mpdostip/html/drdostip.htm |archive-date=2016-11-07}} (NB. Has some information on Symbolic Instruction Debugger (SID86.EXE in DR DOS 3.41 and SID.EXE in DR DOS 5.0/6.0), the predecessor of the DR-DOS DEBUG.EXE.)

{{cite book |title=NWDOS-TIPs — Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |chapter=Kapitel II.5. Allgemeines: Undokumentierte Möglichkeiten von DEBUG |trans-chapter=Undocumented features of DEBUG |work=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=1997-07-30 |edition=3 |version=Release 157 |language=de |url=http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |access-date=2014-09-06 |url-status=live |archive-url=https://web.archive.org/web/20170910194752/http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |archive-date=2017-09-10}} (NB. NWDOSTIP.TXT is a comprehensive work on Novell DOS 7 and OpenDOS 7.01, including the description of many undocumented features and internals. It is part of the author's yet larger MPDOSTIP.ZIP collection maintained up to 2001 and distributed on many sites at the time. The provided link points to a HTML-converted older version of the NWDOSTIP.TXT file.)

{{cite book |title=NWDOS-TIPs — Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |work=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=2001-04-09 |edition=3 |version=Release 183 |language=de}}

{{cite newsgroup |title=SID86 |author-first=Matthias R. |author-last=Paul |date=2002-01-09 |newsgroup=comp.os.cpm |url=https://groups.google.com/d/msg/comp.os.cpm/KG4R7ZNvHK8/U5LAkmjcxYgJ |access-date=2018-04-08 |quote=[…] Since the DR-DOS 7.03 DEBUG is still based on the old SID86.EXE, I suggest to run DEBUG 1.51 and enter the extended help system with ?? from the debug prompt. This will give you eight screens full of syntax and feature help. Some of these features were also supported by older issues. […]}}

{{cite web |url=http://japheth.de/Debug/README.TXT |title=DEBUG README |access-date=2007-06-25 |author-first=Paul |author-last=Vojta |url-status=dead |archive-url=https://web.archive.org/web/20070824025835/http://www.japheth.de/Debug/README.TXT |archive-date=2007-08-24}}

{{cite web|url=http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.2/repos/pkg-html/debug.html |title=FreeDOS 1.2 Updates Package - debug (FreeDOS Base) |publisher=Ibiblio.org |date=2021-02-16 |accessdate=2022-09-08}}

{{cite web |author-first=Vernon C. |author-last=Brooks |title=Enhanced DEBUG for PC DOS and MS-DOS |url=https://pcdosretro.github.io/enhdebug.htm |work=PC DOS Retro |date=2014-04-08 |access-date=2014-05-08 |url-status=live |archive-url=https://web.archive.org/web/20200221141005/https://sites.google.com/site/pcdosretro/enhdebug |archive-date=2020-02-21}}

{{cite book |title=Assembly language for Intel-based computers|url=http://kipirvine.com/asm/debug/Debug_Tutorial.pdf |date=2010 |author-first=Kip R. |author-last=Irvine |isbn=978-0-13602212-1 |edition=6th |publisher=Prentice Hall |section=Using Debug |access-date=2014-03-18}}

[http://bitsavers.org/pdf/intel/ISIS_II/9800306-06_ISIS-II_Users_Guide_May81.pdf ISIS II Users Guide]

[https://archive.org/details/bitsavers_inteliRMX1_19819263 iRMX 86 Introduction And Operator's Reference Manual For Release 6]

{{Cite book |title=TOPS-10 Operating System Commands Manual |date=August 1980 |publisher=Digital Equipment Corporation |url=http://scandocs.trailing-edge.com/tops10-aa-0916d-tb.pdf |access-date=2019-02-17 |archive-date=2020-08-09 |archive-url=https://web.archive.org/web/20200809145058/http://scandocs.trailing-edge.com/tops10-aa-0916d-tb.pdf |url-status=dead }}

{{cite web |url=http://www.textfiles.com/bitsavers/pdf/dec/pdp10/TOPS20/V6.1/AA-FP65A-TM_tops20CmdsRef.pdf |title=TOPS-20 Command manual |access-date=2018-07-18 |archive-date=2020-08-09 |archive-url=https://web.archive.org/web/20200809103116/http://www.textfiles.com/bitsavers/pdf/dec/pdp10/TOPS20/V6.1/AA-FP65A-TM_tops20CmdsRef.pdf |url-status=dead }}

[http://www.bitsavers.org/pdf/phaseOneSystems/THEOS_OASIS_Users_Handbook_1985.pdf THEOS/OASIS User′s Handbook]

[https://www.z80cpu.eu/mirrors/oldcomputers.dyndns.org/public/pub/rechner/zilog/zds/z80-rio_os_userman.pdf Z80-RIO Operating System User's Manual]

{{cite web |url=http://stratadoc.stratus.com/vos/19.1.0/r098-19/wwhelp/wwhimpl/common/html/r098-19.pdf |title=OpenVOS Commands Reference Manual}}

[https://github.com/roelandjansen/pcmos386v501/blob/master/DOCS/v4/PCMOSv4UserManual.pdf PC-MOS User Guide]

{{cite web|url=http://aros.sourceforge.net/documentation/users/shell/index.php|title=AROS Research Operating System}}

{{cite book |title=SID-86 User's Guide for CP/M-86 |date=August 1982 |orig-date=March 1982 |edition=2 |publisher=Digital Research |id=SID86UG.WS4 |url=http://www.cpm.z80.de/manuals/SID86_User_Guide.txt |access-date=2020-02-06 |url-status=live |archive-url=https://web.archive.org/web/20191020123025/http://www.cpm.z80.de/manuals/SID86_User_Guide.txt |archive-date=2019-10-20}} [https://web.archive.org/web/20200208055456/https://archive.computerhistory.org/resources/access/text/2016/12/102762507-05-01-acc.pdf] (NB. A retyped version of the manual by Emmanuel Roche with Q, SR, and Z commands added. This manual is for the CP/M-86 version, but the DR DOS version is similar.)

{{cite magazine |title=Thank You, IBM |author-first=Asael |author-last=Dror |magazine=PC Magazine |date=1988-01-12 |page=366}}

}}

External links

[https://docs.microsoft.com/en-us/previous-versions/tn-archive/cc722863(v=technet.10) Debug | Microsoft Docs]
[https://github.com/microsoft/MS-DOS/blob/master/v2.0/source/DEBUG.ASM Open source DEBUG implementation that comes with MS-DOS v2.0]

Category:Assemblers

Category:Debuggers

Category:Disassemblers

Category:External DOS commands

Category:Microsoft free software

Category:OS/2 commands