The wakeup statement is used for BASIC programs to wake up a different process that is either sleeping or waiting for input at an INPUT statement (which has an associated ELSE clause).
WAKEUP process.no THEN/ELSE ....
When the specified process wakes up, it executes the next statement in that program. If the specified process was waiting for input, it takes the ELSE clause of the INPUT statement. In either case, SYSTEM(0) can be used to determine which process woke it up.