Use the Toggle Breakpoint command to turn breakpoints
(places you want your program to stop running) on and off:
  1. Move the cursor to the line you want the breakpoint on.
  2. Choose Toggle Breakpoint (or press F9).
QuickBASIC highlights the breakpoint line.
 
To turn off a breakpoint:
  1. Move the cursor to a highlighted breakpoint line.
  2. Choose Toggle Breakpoint.
 
Use a breakpoint to pause your program at a point where
you suspect problems, then
  - Test the values of variables in the Immediate window
    or with Instant Watch
  - Add variables to the Watch window and single step your
    program from the breakpoint forward