Four Components of a Computer System

Abstract view of the components of a computer system.

A computer system can be divided into four components:

• hardware — CPU, memory, I/O devices; provide computing resources
• operating system — controls hardware, coordinates its use among applications and users
• application programs — how the resources are used to solve users’ computing problems
• users — people, machines, other users

What Operating Systems Do

The user’s view of the computer depends on how they are interfacing with the system.

If the resources of the computing system are being used by a single user, then:

• the OS is designed for ease of use
• is not concerned with resource utilization (how hardware & software resources are shared)

If the resources are shared between multiple users, then:

• the OS is designed for resource utilization

Should the system have its own dedicated resources, but also share some resources with other workstations (such as file and print servers), then the OS is designed to compromise between ease of use and resource utilization.

• More information, if needed.

Defining Operating Systems

The operating system is a resource allocator — it manages the various resources of the computer system. The OS must decide how to allocate these resources to specifics programs & users in an efficient and fair manner.

The OS as a control program, which is responsible for managing user program execution, preventing errors and improper use, as well as the control and operation of I/O devices.