In computing, scheduling is the method by which work specified by some means is assigned to resources that complete the work. The work may be virtual computation elements such as threads, processes or data flows, which are in turn scheduled onto hardware resources such as processors, network links or expansion cards.
A scheduler may aim at one or more of many goals, for example: maximizing throughput (the total amount of work completed per time unit); minimizing wait time (time from work becoming enabled until the first point it begins execution on resources); minimizing latency or response time (time from work becoming enabled until it is finished in case of batch activity, or until the system responds and hands the first output to the user in case of interactive activity);or maximizing fairness (equal CPU time to each process, or more generally appropriate times according to the priority and workload of each process). In practice, these goals often conflict (e.g. throughput versus latency), thus a scheduler will implement a suitable compromise.
A process is an instance of a program running in a computer. It includes the current values of the program counters, all the registers, and also the variables. The processes waiting to be assigned to a processor are put in a queue called ready queue. Burst time is amount of time for which a process is being held by the CPU. When a process arrives at the ready queue it is the arrival time. From the time a process is submitted to the time it is completed is the turnaround time. When a process waits in the ready queue that time is the waiting time. The number of times CPU gets switched from a process to another one is called context switching. The optimal and the best scheduling algorithm will have less waiting time, less turnaround time and less number of context switches.