CPU Scheduler

We had much experience for waiting. Recently, in bank, we get a unique number entering the bank. There several line processing at the same time. Once the number flip, somebody will be served. A small version of same thing happens on our operating system. Lots of process standby for being served. The main difference was we have just one cpu at most time. For simplicity, we also consider the situation with one cpu which mean there is always one process being served at one time.
Short-term scheduler , a intermediator for dispatching a process to use the cpu resource. One choose a process from free-memory and one from secondary storage device to memory is the difference between short-term scheduler and long-term scheduler(also called job scheduler).
Activity of process of the operatiing system exist all the time. However, there is only one cpu can be used. Therefore a process can be run at one time.The way directly perceived through the senses and simplist is first in first serve which means one process one by one served by cpu a time until no one is waiting.Forgeting bank number will cause a seriel wait when he need call for his family for help. Part of service of next people can proceed to shorten total waiting time.
A lot of scheduling method be brought up like Round-Rubin , FCFS(First come first serve), SJF(Shortest Job First) , Multilevel feedback queue scheduling.I implemented four of them in Java with fully architecture include virtual cpu, virtual timing.