A breakpoint is a location in your program at which you want execution
  to stop so that you can check the current value of a variable, step
  into a routine, and so on.

  When using the debugger's DECwindows Motif interface, you can set
  breakpoints on:

   -  Specific source lines

   -  Specific routines (functions, subprograms, and so on)

   -  Specific instructions (displayed in the instruction view)

   -  Exceptions signaled during the execution of your program

  The debugger provides two ways to qualify breakpoints:

   -  You can set a conditional breakpoint.  It triggers only when a
      specified relational expression is evaluated as true.

   -  You can set an action breakpoint.  It executes one or more
      specified system-specific commands when the breakpoint triggers.

  You can set a breakpoint that is both a conditional and action
  breakpoint.