DEBUG.COM is a DOS efficacy that facilitates the trouble-shooting and debugging of assembly language programs. In particular case of personal computers, all of the resources, processor and memory resource management functions are carried out by the operating systems. Therefore, users have very little control on the computer hardware at lower levels. The DEBUG efficacy enables you to have the control of these resources up to some extent. In the easier, rather then, basic words, the DEBUG enable you to use the personal computer as a low level microprocessor kit.
The DEBUG command at DOS prompt invokes this facility. A '_' (dash) display signals the successful invoke operation of DEBUG, further that is used as DEBUG prompt for debugging commands. Following command line, DEBUG prompt and the DEBUG command character display describe the DEBUG command entry procedure, as in given Figure.
A valid command is accepted by using the enter key. The list of typically used valid commands of DEBUG is given in Table namely DUBEG command along with their respective syntax.
The program DEBUG can be used either to debug a source program or to view the results of execution of an .EXE file with the help of the .LST file and the above commands. The .LST file indicates the offset address allotments for result variables of a program in the specific segment. After the execution of the program is completed the offset address of the result variables can be observed by using the d command. The results available in the registers may be view by using the r command. So the DEBUG offers a reasonably good platform for trouble-shooting executing and observing the results of the assembly language programs. Here one should remember that the DEBUG is able to only trouble-shoot the .EXE files.