These are buttons Start/Stop, Lap, Reset
Start/Stop - Keyboard Equivalent = Space
Click on 'Start' to start the Stopwatch. This button will then change and read 'Stop'. Now click this button to stop the stopwatch.
This button is only available when the stopwatch is running. Click on this button to record the time to the tape display.
This button is only available when stopwatch has been started and stopped. Click on this button to reset the stopwatch.