24. Simulated duff TV
    ~~~~~~~~~~~~~~~~~
This routine gives the fairly convincing impression that your TV or monitor
has gone duff, especially if you turn the brightness up a bit. If you have a
Master or Compact, then the ",0;0;0;" bit can be replaced by the single
character '|'. Someone suggested hiding it somewhere in a program, as a booby
trap for your mates....

10 VDU23,0,RND(255),RND(255),0;0;0;:GOTO 10