Debug--Notes

Using the debug command without specifying a file to be tested

If you use the debug command without a location and filename, you then type all Debug commands in response to the Debug prompt, a hyphen (-).

Debug commands

The following is a list of Debug commands.

?	Displays a list of the Debug commands.
a	Assembles 8086/8087/8088 mnemonics.
c	Compares two portions of memory.
d	Displays the contents of a portion of memory.
e	Enters data into memory starting at a specified address.
f	Fills a range of memory with specified values.
g	Runs the executable file that is in memory.
h	Performs hexadecimal arithmetic.
i	Displays one byte value from a specified port.
l	Loads the contents of a file or disk sectors into memory.
m	Copies the contents of a block of memory.
n	Specifies a file for an l or w command, or specifies the parameters for the file you are testing.
o	Sends one byte value to an output port.
p	Executes a loop, a repeated string instruction, a software interrupt, or a subroutine.
q	Stops the Debug session.
r	Displays or alters the contents of one or more registers.
s	Searches a portion of memory for a specified pattern of one or more byte values.
t	Executes one instruction and then displays the contents of all registers, the status of all flags, and the decoded form of the instruction that Debug will execute next.
u	Disassembles bytes and displays the corresponding source statements.
w	Writes the file being tested to a disk.
xa	Allocates expanded memory.
xd	Deallocates expanded memory.
xm	Maps expanded memory pages.
xs	Displays the status of expanded memory.

Separating command parameters

All Debug commands accept parameters, except the q command. You can separate parameters with commas or spaces, but these separators are required only between two hexadecimal values. Therefore, the following commands are equivalent:

dcs:100 110

d cs:100 110

d,cs:100,110

Specifying valid address entries

An address parameter in a Debug command specifies a location in memory. Address is a two-part designation containing either an alphabetic segment register or a 4-digit segment address, plus an offset value. You can omit the segment register or segment address. The default segment for the a, g, l, t, u, and w commands is CS. The default segment for all other commands is DS. All numeric values are in hexadecimal format.

The following are valid addresses:

CS:0100

04BA:0100

The colon between the segment name and the offset value is required.

Specifying valid range entries

A range parameter in a Debug command specifies a range of memory. You can choose from two 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

More Information About Debug

Debug Commands

Debug