The
Monitor
ä Monitor reads jobs one at a
time from the input device
ä Monitor places a job in the user
program area
ä A monitor instruction branches
to the start of the user program
ä Execution of user pgm
continues until:
ä end-of-pgm occurs
ä error occurs
ä Causes the CPU to fetch its
next instruction from Monitor
ä OS:
ä Alternates execution between
user program and the monitor
program
ä Relies on available hardware
to effectively alternate
execution from various parts
of memory