Line 2000-2510 assemblies keyboard entries and sends them to the MMI at the Enter key ( CR = carriage return or enter key). Note the special commands at line 2210-2270 which are created commands not part of the MMI command set.
Line 2600-2750 reads any incoming characters from the MMI and prints to the host display screen.
Line 2910-3000 closes the comm ports on Exit (F5) or a computer error code other than ERROR = 24 (comm port is busy).
Line 3000-3150 writes zeros (545 stop command) and carriage returns over the entire memory (Clear command) which erases the memory. The opposite is the Load command which writes the memory.
Line 3300-3400 is the busy error routine.
Line 4000- are the help files.