Comparison between Schedules
S.N. Long Term Scheduler Short Term Scheduler Medium Term Scheduler
1 It is a job scheduler It is a CPU scheduler It is a process swapping scheduler.
2 Speed is lesser than short term
scheduler
Speed is fastest among other
two
Speed is in between both short and
long term scheduler.
3 It controls the degree of
multiprogramming
It provides lesser control over
degree of multiprogramming
It reduces the degree of
multiprogramming.
4 It is almost absent or minimal in
time sharing system
It is also minimal in time
sharing system
It is a part of Time sharing systems.
5 It selects processes from pool and
loads them into memory for
execution
It selects those processes
which are ready to execute
It can re-introduce the process into
memory and execution can be
continued.
Operation on process
1. Process creation: A user requests, and already running process can creates new
processes. Parent process creates children processes using a system call, which, in
turn create other processes, forming a tree of processes.
2. Process preempting: A process preempted if I/O event or timeout occurs. Then
process moves from running state to ready state and CPU loads another process
from ready state to running state, if available.
3. Process blocking: When a process needs I/O event during its execution, then
process moves from running state to waiting state and dispatches another process
to CPU.
4. Process termination: A process terminated if when a process completes its
execution. Also, these events: OS, Hardware interrupt, and Software interrupt can
cause termination of a process.
