Debug (command)

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DEBUG.COM (MS-DOS <= 2.0), DEBUG.EXE (MS-DOS >= 3.x)
Original authorTim Paterson
DevelopersMicrosoft, IBM, Digital Research, Novell, Caldera
Repository
  • {{URL|example.com|optional display text}}Lua error in Module:EditAtWikidata at line 29: attempt to index field 'wikibase' (a nil value).
Written inMS-DOS: x86 assembly language
Engine
    Lua error in Module:EditAtWikidata at line 29: attempt to index field 'wikibase' (a nil value).
    Operating systemDOS, OS/2, Windows
    TypeDebugger
    LicenseMS-DOS v2.0, FreeDOS: MIT
    OS/2, Windows: Proprietary software
    WebsiteDebug

    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[1]).

    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

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    DEBUG.COM (among other commands) in IBM PC DOS 1.0.
    The Microsoft Windows 95 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] 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 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.[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.[3]

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

    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,[4] which came with former versions of DR DOS.[5][6][7] 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.[8][7] Some versions also utilized DPMS to function as a "stealth mode" protected-mode debugger.[9]

    The FreeDOS version of DEBUG was developed by Paul Vojta and is licensed under the MIT License.[10]

    A 32-bit clone "DEBUGX" version supporting 32-bit DPMI programs exists as well.[11] 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.[12]

    Syntax

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    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.[13] 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.[14] This method can be used to create or edit binary files from batch files.[2]

    Using for non-debugging purposes

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    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

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    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.[15]

    Other operating systems

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    The operating systems Intel ISIS-II[16] and iRMX 86,[17] DEC TOPS-10[18] and TOPS-20,[19] THEOS/OASIS,[20] Zilog Z80-RIO,[21] Stratus OpenVOS,[22] PC-MOS,[23] and AROS[24] also provide a DEBUG command.

    See also

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    References

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    1. ^ According to Microsoft Macro Assembler Reference, inline assembly is not supported for x64.
    2. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    3. ^ MS-DOS subsystem commands
    4. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). [1] (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.)
    5. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). (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.)
    6. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). (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.)
    7. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    8. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). (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.)
    9. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    10. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    11. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    12. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    13. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    14. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    15. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    16. ^ ISIS II Users Guide
    17. ^ iRMX 86 Introduction And Operator's Reference Manual For Release 6
    18. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    19. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    20. ^ THEOS/OASIS User′s Handbook
    21. ^ Z80-RIO Operating System User's Manual
    22. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    23. ^ PC-MOS User Guide
    24. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
    [edit | edit source]
    Wikibooks has a book on the topic of: Guide to Windows Commands
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