Page 9 - DCAP403_Operating System

Operating System

Notes 1.1 Operating System: Meaning

An operating system (sometimes abbreviated as “OS”) is the program that, after being initially
loaded into the computer by a boot program, manages all the other programs in a computer.
The other programs are called applications or application programs. The application programs
make use of the operating system by making requests for services through a defi ned Application
Program Interface (API). In addition, users can interact directly with the operating system
through a user interface such as a command language or a Graphical User Interface (GUI).
Figure 1.1: Operating System Interface

Hard Drive

Computer
Mouse Operating System
Monitor
Video Card

Sound Card
Keyboard Speakers

In a computer system, you find four main components: the hardware, the operating system,

the application software and the users. In a computer system, the hardware provides the basic
computing resources. The applications programs define the way in which these resources are

used to solve the computing problems of the users. The operating system controls and coordinates
the use of the hardware among the various systems programs and application programs for the
various users.
You can view an operating system as a resource allocator. A computer system has many resources
(hardware and software) that may be required to solve a problem: CPU time, memory space,

files storage space, input/output devices etc. The operating system acts as the manager of these
resources and allocates them to specific programs and users as necessary for their tasks. Since

there may be many, possibly conflicting, requests for resources, the operating system must decide

which requests are allocated resources to operate the computer system fairly and effi ciently.
An operating system is a control program. This program controls the execution of user programs
to prevent errors and improper use of the computer. Operating systems exist because: they are
a reasonable way to solve the problem of creating a usable computing system. The fundamental
goal of a computer system is to execute user programs and solve user problems.

While there is no universally agreed upon definition of the concept of an operating system, the
following is a reasonable starting point:
A computer’s operating system is a group of programs designed to serve two basic purposes:
1. To control the allocation and use of the computing system’s resources among the various
users and tasks, and
2. To provide an interface between the computer hardware and the programmer that simplifi es
and makes feasible the creation, coding, debugging, and maintenance of application
programs.

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