Debug Commands

In the summary below: addr  is XXXX  -OR-  XXXX:XXXX -OR- segreg:XXXX
                      range is addr,addr  -OR-  addr L byte_count
                      value is XXXX
                      port  is XX
All numbers, values, counts, and addresses must be in hexadecimal notation.

Command               Function
────────────────────  ──────────────────────────────────────────────────────
?                     Help.  List command syntax

A [addr]              Assemble.  Enter assembly language mnemonics; press
                       on a blank line to stop entering code

C range addr          Compare blocks of memory

D [addr]              Display (dump) memory in hex and ASCII

E addr [bytes]        Enter (edit) bytes and strings into memory

F range bytes         Fill memory with pattern of bytes

G [=addr] [[addr]...] Go.  Execute code at CS:IP (or at =addr) with
                      optional breakpoints at indicated addresses

H value1 value2       Hexarithmetic. Display value1+value2 and value1-value2

I port                Input.  Display value of an INP for indicated port

L [addr]              Load.  Load file of Name at indicated addr or CS:100
L [addr] drv sec cnt  Load cnt absolute disk sectors from drive drv, sector
                      sec into memory starting at address addr (or CS:100)

M range addr          Move block of memory to addr

N d:file [parms]      Name.  Set up for Load or Write with file and parms

O port byte           Output a byte to a port

P [=addr][count]      Proceed.  Single-step execute a CALL, LOOP, INT, etc.

Q                     Quit.  Exit from Debug

R [register]          Registers.  Displays current values.  Allows input
                      of values to a register or Flags.  It also sets for
                      next Unassemble to start at CS:IP.

S range bytes         Search memory.  Show addrs that contain the bytes

T [=addr][count]      Trace.  Single-step execute count opcodes (or 1)

U [addr] or [range]   Unassemble.  Display opcode mnemonics at addr (or 128
                      bytes starting at last addr Unassembled)

W [addr]              Write from memory to file named in previous Name
                      command or the initial file).  Writes starting from
                      addr (or CS:100) for size in BX:CX

W [addr] drv sec cnt  Write cnt absolute disk sectors from memory starting
                      at addr.  Start writing at sector sec of drive drv

XA count              eXpanded mem Allocate count 16K pages of EMS memory
XD handle             eXpanded mem Deallocate EMS pages of handle
XM lpage ppage handle eXpanded mem Map logical EMS page to physical page
XS                    eXpanded mem Status.  Display status of EMS memory

See Also: 80x86/87 Opcodes
          TECH Topics