4.4.2 Determining the Current Location of the Program
            Counter
  The SHOW CALLS command lets you determine the cur-
  rent location of the program counter (PC) (for example, after
  returning to the debugger following a Ctrl/Y interrupt). The
  command shows a traceback that lists the sequence of calls
  leading to the currently executing routine. For example:
  DBG> SHOW CALLS
    module name routine name line rel PC abs PC
  *TEST PRODUCT 18 00000009 0000063C
  *TEST COUNTER 47 00000009 00000647
  *MY_PROG MY_PROG 21 0000000D 00000653
  DBG>

  For each routine (beginning with the currently executing
  routine), the debugger displays the following information:

  .
        The name of the module that contains the routine
  .
        The name of the routine
  .
        The line number at which the call was made (or at which
        execution is suspended, in the case of the current routine)
  .
        The corresponding PC addresses (the relative PC address
        from the start of the routine and the absolute PC address
        of the program)

  This example indicates that execution is currently at line 18
  of routine PRODUCT (in module TEST), which was called
  from line 47 of routine COUNTER (in module TEST), which
  was called from line 21 of routine MY_PROG (in module
  MY_PROG).