Watchpoints A watchpoint is a signal that tells the debugger to pause the program when the value of an expression changes. Set a watchpoint Watchpoints can be set to stop program execution each time the value of an expression changes. In order to set the watchpoint, the program must be running in the Debugger. Conditional watchpoints You can specify that the watchpoint is conditional, using a Boolean expression to determine whether to stop execution of the program when the variable value has changed.