Debug: U (Unassemble)

Page updated January 21, 2005

Disassembles bytes and displays their corresponding source statements, including addresses and byte values. The disassembled code looks like a listing for an assembled file. Used without parameters, u disassembles 20h bytes (the default number), beginning at the first address after the address displayed by the previous u subcommand.

Syntax

u [Range]

Parameters

Range

Specifies the starting and ending addresses, or the starting address and length, of the code you want to disassemble.

Displays a list of debug subcommands.

Remarks

Windows XP and the Windows Server 2003 family of products do not use this command. It is included only to preserve compatibility with existing MS-DOS files, but it has no effect at the command line because the functionality is automatic.
Use Range with a debug subcommand to specify a range of memory. You can choose one of the following formats for Range: a starting address and an ending address, or a starting address and the length (denoted by l) of the range. For example, both of the following syntaxes specify a 16-byte range beginning at CS:100:

cs:100 10f

cs:100 l 10
For information about assembling mnemonics by using the a (assemble) subcommand, see Related Topics.
For information about displaying the contents of a portion of memory by using the d (dump) subcommand, see Related Topics.

Examples

To disassemble 16 (10h) bytes, beginning at address 04BA:0100, type:

u04ba:100l10

Debug.exe displays the results in the following format:

04BA:0100 206472 AND [SI+72],AH

04BA:0103 69 DB 69

04BA:0104 7665 JBE 016B

04BA:0106 207370 AND [BP+DI+70],DH

04BA:0109 65 DB 65

04BA:010A 63 DB 63

04BA:010B 69 DB 69

04BA:010C 66 DB 66

04BA:010D 69 DB 69

04BA:010E 63 DB 63

04BA:010F 61 DB 61

To display only the information for the specific addresses 04BA:0100 through 04BA:0108, type:

u04ba:0100 0108

Debug.exe displays the following:

04BA:0100 206472 AND [SI+72],AH

04BA:0103 69 DB 69

04BA:0104 7665 JBE 016B

04BA:0106 207370 AND [BP+DI+70],DH

Formatting legend

Format	Meaning
Italic	Information that the user must supply
Bold	Elements that the user must type exactly as shown
Ellipsis (...)	Parameter that can be repeated several times in a command line
Between brackets ([])	Optional items
Between braces ({}); choices separated by pipe (\|). Example: {even\|odd}	Set of choices from which the user must choose only one
Courier font	Code or program output

Some of these terms may be the same or similar to DOS commands. For information on DOS Commands, click here

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