This routine controls the printing of error and control messages by the KERNAL. Either print error messages or print control messages can be selected by setting the accumulator when the routine is called. FILE NOT FOUND is an example of an error message. PRESS PLAY ON CASSETTE is an example of a control message.

Bits 6 and 7 of this value determine where the message will come from.

If bit 7 is 1, one of the error messages from the KERNAL is printed.

If bit 6 is set, control messages are printed.

If this is set to 0 then all kernal messages are disabled.