53279    $D01F    CONSOL

Read
User to look up if any of the 3 console keys (START, SELECT, OPTION) has been pressed (RESET is not a console keys, neither is [HELP]) 

START    Bit 0    PEEK(53279)=6

SELECT   Bit 1    PEEK(53279)=5

OPTION   Bit 2    PEEK(53279)=3


Write
The built in speaker clicks (only on 400/800 computers)