Computer Science UGC Net

Preemptive Scheduling : In contrast to non preemptive scheduling, a scheduling decision can be made even while the job is executing whereas in non preemptive scheduling, a scheduling decision is made only after job completes its execution. Therefor preemptive scheduling may force a job in execution to release the processor, so that the execution of some other job can be undertaken, in order to improve throughput considerably. Types of preemptive scheduling: 1) Round Robin scheduling algorithm : the round Robin scheduling is designed for time sharing systems. The primary objective of round Robin scheduling are interactive use, good response time and sharing the resources equitable among processes. It is similar to FCFS, but preemption is added to switch between processes. The processes are alocated a small unit of time. Known as time Quantum or time slice is in rotation until the completion of processes. To implement round Robin scheduling, a FIFO(first in first out) queue...

Scheduling : In multi-programmed computer, multiple processes competing for the CPU at the same time. This situation occurs whenever two or more processes are simultaneously in the ready state. If only one CPU is available. Then we need a system that decide which process run first and then next and this will be done by the scheduler. Scheduler : scheduler is an operating system module that she loves an axe top to be admitted into the system and then the next process to run. Scheduling is of two type: 1) Pre-emptive 2) Non pre-emptive Non Pre-emptive Scheduling : In batch non Pre-emptive scheduling implies that, once scheduled, selected job runs to completion. In other words, the running process not forced to relinquish ownership of the processor when a higher priority process becomes ready for execution. The scheduling techniques which use non preemptive scheduling are: 1) first come first serve (FCFS) scheduling 2) shortest job next (SJN) scheduling 3) dea...

"An Operating System is an interface between the computer user and the computer hardware". An operating system is an program that manages the computer hardware.Basically, a computer system can be divided roughly into four components the hardware the operating system the application programs and the users. It controls and coordinate the use of hardware among the various application programs for various users. We have various operating systems available. Some popular operating system are: Linux, Unix, windows operating system which is mostly used these days, MAC operating system (specifically used by "apple"). Main Functions of Operating System: 1. Process management 2. Main Memory management 3. File management 4. Input/Output management 5. Secondary storage management Process Management: A program is a passive entity such as content of a file stored in disk, whereas a process is an active entity, with a program counter specifying the ne...