DOS/32 Advanced DOS Extender - Technical Reference

6.0 - DOS/32 Advanced - Built-in Debugger

Another feature of DOS/32 Advanced DOS Extender is that you can use the software breakpoints INT 1 and INT 3 to debug your programs without any external debugger. When the program execution reaches a software breakpoint, DOS/32 Advanced will:

1) save the state of the machine
2) switch to internal stack
3) restore real mode IRQ 1 (keyboard)
4) display the state of the machine
5) prompt you to select an action

if Abort is selected:
6) return to DOS

if Proceed or Trace are selected:
6) restore the previously installed IRQ 1
7) restore the state of the machine
8) return to the program execution

The debugger will ask you to press the key 'P' to proceed with execution of your program from the place where the breakpoint was encountered, the key 'A' to abort and exit to DOS or the key 'T' to single step through your application. Each time you press the 'T' key, a single CPU instruction will be executed, and the debugger will be reentered showing the new state of the machine.

Note that this built-in "debugger" does not require any extended memory, it does not take up any of the system's resources, and it does not use any external programs. This is just a simple and easy to use tool for the system programming when an external debugger does not do the job.


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