1. You must compile your binary objects with -g option firstly.
2. link your objects to a executable program.
3. dbx -I /home/path1  -I /home/path2 .....
    to specify all source code path, so that dbx can find the relevant source code and dispay it for you.

4.dbx shows a prompt:
   enter object file name (default is `a.out', ^D to exit):
   enter the program name.
5. now you can use below command to debug you program.

   stop at  43/*line number*/ /*set break point*/
   clear /*remove all break points*/
   cont /*continue the execution of the program*/
   next /*run to next line*/
   step /*step in*/
   run
   rerun
   print /*print the content of a variable*/
   file /*show current source file name, you can use the command to specify a new source file*/
   where /*show the function calling stack*/