Debug Code
You can narrow down problem areas in your code using breakpoints in the IDL Editor. A breakpoint suspends the execution of a program at the location of the breakpoint. During program execution, when the program encounters a breakpoint, IDL displays a dialog asking if you want to display the Debug Perspective.
For complete information, please see Debugging Tools.
To set a breakpoint in the IDL Editor, find the line where you want to place the breakpoint, and double-click in the gutter to the left of the line. Breakpoints display as blue circles, as shown below:

To delete a breakpoint, just double-click on it.
To disable the breakpoint but not delete it, right-click on the breakpoint icon and select Disable Breakpoint from the pop-up menu. This action disables the breakpoint but leaves a white circle marker. A disabled breakpoint will not cause threads to suspend.
Tip
You can also Toggle breakpoints by right-clicking in the gutter to the left and selecting Toggle Breakpoint from the pop-up menu.
Accessing the Breakpoints View
The Breakpoints view allows you to manage your code breakpoints. To display this view, select Window → Show View → Breakpoints.

In the Breakpoints view you can control your breakpoints, easily find the breakpoints in multiple files, and choose how to group them in the display.
For more information, see "Breakpoints View" and "Debugging and Error Handling."