Setting a breakpoint

A basic breakpoint indicates a stopping point in your program. For example, to stop on line 100 of your program, enter the following command on the command line:

AT 100

In the Log window, the message AT 100 ; appears. If line 100 is not a valid place to set a breakpoint, the Log window displays a message similar to Statement 100 is not valid. The breakpoint is also indicated in the Source window by a reversing of the colors in the prefix area.

Breakpoints do more than just indicate a place to stop. Breakpoints can also contain instructions. For example, the following breakpoint instructs z/OS Debugger to display the contents of the variable myvar when z/OS Debugger reaches line 100:

AT 100 LIST myvar;

A breakpoint can contain instructions that alter the flow of the program. For example, the following breakpoint instructs z/OS Debugger to go to label newPlace when it reaches line 100:

AT 100 GOTO newPlace ;

A breakpoint can contain a condition, which means that z/OS Debugger stops at the breakpoint only if the condition is met. For example, to stop at line 100 only when the value of myvar is greater than 10, enter the following command:

AT 100 WHEN myvar > 10;

A breakpoint can contain complex instructions. In the following example, when z/OS Debugger reaches line 100, it alters the contents of the variable myvar if the value of the variable mybool is true:

AT 100 if (mybool == TRUE) myvar = 10 ;

The syntax of the complex instruction depends on the program language that you are debugging. The previous example assumes that you are debugging a C program. If you are debugging a COBOL program, the same example is written as follows:

AT 100 if mybool = TRUE THEN myvar = 10 ; END-IF ;