ON Keyword - Different Uses
 
The ON keyword is used in various statements to trap events:
Specifies a trap          Type of event                    Enables the trap
<ON COM(N)>         events on communications port n          <COM(N) ON>
<ON KEY(N)>         a keystroke on key n                     <KEY(N) ON>
<ON PEN>            lightpen events                          <PEN ON>
<ON PLAY(N)>        less than n notes in music buffer        <PLAY ON>
<ON STRIG(N)>       events on joystick trigger n             <STRIG(N) ON>
<ON TIMER(N)>       timer events                             <TIMER ON>
<ON UEVENT>         user-defined events                      <UEVENT ON>
 
Other uses of the ON keyword are:
<ON ERROR> - to enable error handling and specify the error-handling routine
<ON...GOSUB> - to branch to one of a list of subroutines
<ON...GOTO>  - to branch to one of a list of line labels