Process Scheduler, schedules different processes to be assigned to the CPU based on some algorithms for the scheduling. There are six well-known process scheduling algorithm, which we will discuss in this chapter. 

  • First-come, first-served (FCFS)
  • Scheduling Shortest-Job-Next (SJN) 
  • Priority Scheduling 
  • The Shortest Amount Of Time Remaining In The 
  • Round-robin Scheduling (RR)
  • The Multi-level queue scheduling 

These algorithms are no pre-emptive rights, or they are also on prevention. Non-transitive algorithms are constructed in such a way that, when one process that contains a running state, it cannot be preempted, it will still not be allowed to complete the tasks allocated to it at the time, while a pre-emptive scheduling is based on the benefit which the scheduler is able to tell the one running with a low priority for the time when, as a high-priority process is complete. 

First-come-first-served (FCFS) 

  • The data is performed on a first-come, first-served basis. 
  • This is a warning, and the pro-active scheduling algorithm. 
  • An easy to understand and implement. 
  • The implementation is based on FIFO queue. 
  • Poor performance, so that the average wait time is high. 

Waiting time of each is as follows:  


Average wait time is (0+4+6+13)/4 = 5.75

The shortest amount of work experience is the Next - (SJN) 

  • And, you know, it's the shortest job first, or SJF 
  • This is a warning, and the pro-active scheduling algorithm. 
  • The best way to minimize the lag. 
  • It's easy to figure out from the system and the package of the processor time is required in   advance. 
  • Impossible, exercises, and interactive system in which you would like to, CPU time, and the   unknown. 
  • The operator should know in advance how long the process will take. 

Given: A table of processes and their actual arrival on the run 

Waiting time of each is as follows:  

Average wait time is (0+4+12+5)/4 = 5.25

Priority-Based Scheduling 

  • Priority-based scheduling, rather than the prevention of the algorithm, and is one of the most   common of the party of the scheduling algorithms in the system. 
  • Each of the process is to be preferred. The process with the highest priority and should be   implemented first, and so on. 
  • Processes with same priority are executed on a first-come, first-served basis. 
  • The priority may be based on memory, time, or other resources. 

Given: A table of processes and their time of arrival at the time of driving, and as a priority. Here, we look at a 1, which is a very high priority. 



Waiting time of each is as follows:  



Average wait time is (0+10+12+2)/4 = 6

The Shortest Amount Of Time Remaining.

  • Shortest remaining time (SRT) is the preemptive version of the SJN algorithm. 
  • The CPU is allocated to the work of the closest in the end, however, it can be prevented by a newer version of this issue, for a short period of time to complete. 
  • Impossible, exercises, and interactive system in which you would like to, CPU time, and the unknown. 
  • It is often used in contexts in which the short descriptions are to be preferred. 

Cyclic Scheduling 

  • The Ridge, however, is very useful, an algorithm for the prevention of the process of scheduling. 
  • Each process is managed in a solid performance period of time, it is called a quantum. 
  • When a process is executed for a certain period of time, it is preempted and other process, which is carried out for a certain period of time. 
  • In the context of the transition, also is used to save states of America, and the offset process. 
Waiting time of each is as follows:  

Average wait time is (9+2+12+11)/4 = 8.5

The Multi-level queue scheduling 

It is a turn-by-turn strategy, independent of the scheduling algorithm. They are likely to make use of existing algorithms for the purpose of grouping and scheduling of jobs with a common characteristic. 

  • The processes, which are a common feature of multiple queues are supported. 
  • Each, in turn, may have its own algorithm for scheduling. 
  • Priorities are assigned to each person, in turn, one after the other. 
For example, the CPU-related information can be planned in stages, however, all of the input-output-based tasks are different. After that, the process, task scheduler, take it in turns to choose a job, each and every one of them in turn and assign them to the processor based on the role of algorithms.