-A 100 0AF7:0100 MOV AH, 4C 0AF7:0102 INT 21 0AF7:0104 [Press Enter] Now run it with G (Go). The program will exit back to DEBUG. To see what’s at address 0100 :
Happy debugging.
Whether you’re learning low-level programming, repairing old software, or just curious how DOS worked, DEBUG is a tool worth mastering. Now that you have it downloaded and configured, start with the examples above and explore the rest with ? (the help command inside DEBUG). Download Debug Exe For Dosbox Windows
Introduction For decades, DEBUG.EXE has been an essential tool for programmers, reverse engineers, and retro-computing enthusiasts. Originally bundled with MS-DOS, this simple yet powerful machine-level debugger allows you to examine memory, disassemble code, write assembly instructions, and troubleshoot programs at the hardware level.
To change a register value, e.g., set BX to 1234 : -A 100 0AF7:0100 MOV AH, 4C 0AF7:0102 INT
U 100 104 Output:
R BX DEBUG will show the current value and wait for a new hex value. Type 1234 and press Enter. Let’s write a one-instruction program that exits cleanly: Introduction For decades, DEBUG
C:\DOS> DEBUG You should see a single dash - prompt. That’s it – you are now inside the debugger.
AX=0000 BX=0000 CX=0000 DX=0000 SP=FFEE BP=0000 SI=0000 DI=0000 DS=0AF7 ES=0AF7 SS=0AF7 CS=0AF7 IP=0100 NV UP EI PL NZ NA PO NC 0AF7:0100 CD20 INT 20 This shows all 16-bit registers and the next instruction to execute.
Type Q and press Enter to quit back to DOS. Part 6: Basic DEBUG Commands (with Examples) Here are the essential commands to get you started. Each command is a single letter followed by optional parameters. 1. View CPU Registers – R Type R and press Enter. You’ll see: