Operating systems are an important part of almost all computer systems. Computer systems can be roughly divided into four parts: hardware, operating systems, applications and users.
The basic purpose of a computer system is to execute user programs and solve user problems more easily.. To achieve this goal, a computer hardware is constructed. Because hardware alone is not necessarily easy to use, applications have been developed. These applications require some common operations, such as controlling I/O devices. These functional sets that jointly control and allocate I/O device resources constitute a software module: the operating system.
A widely recognized definition is that an operating system is a program (usually called a kernel) that has been running on a computer, while other programs are applications.
The operating system and computer architecture have a great influence on each other. To facilitate the use of hardware, the researchers developed an operating system. Users of the operating system also propose improvements to the hardware design to simplify the operating system. Through a brief historical review, it is often noted that the discovery of problems in the operating system will lead to the introduction of new hardware features.
The most important aspect of Job Scheduling is the ability to implement multiple programs. A single user is usually not busy with CPU and I/O devices. Multi-channel program design by organizing jobs so that the CPU has a total of jobs that can be executed, thus improving the CPU utilization.