This is a set of programs which takes over the operation of the computer to the point of being able to allow a number of programs to be run on the computer without intervention by an operator.

It acts as an interface between the user and the hardware. It controls and allocates hardware resources on the computer.  Examples are MS DOS, MS Window, Linux, Unix, Novell, Macintosh, PC DOS, Android, etc.


  • It serves as the communication link between user and the hardware.
  • It controls selection and operation of input and output devices.
  • It handles file operation
  • It gives a complete record of all that happens during processing.
  • It schedules and loads jobs in order to provide for continuous processing.
  • It controls system security by monitoring the use of password.
  • It will organizes files on a variety of storage media
  • It manages hardware error and loss of data
  • It facilitate passing of control from one program to another without human intervention.
  • It allocate facilitates to files and programs.


Types of operation systems

Operating system can be classified using different criteria. Based on the number of processes allowed to run, operating system can be grouped into.

  • Single-user operating system
  • Multi-user operating system
  • Network operating system
  1. Single-user/single task operating system: This is an operating system designed for only one user at a time. It can also carry out a single task operation at a time. For instance, when a computer is printing a document, it commands until printing is completed.

Example of single task OS is MS DOS. It is a single-user, single-task operating system design by Microsoft Inc. to oversee operations such as input and output, video support and many internal functions related to program execution and file maintenance.

  1. Multi-user/Multi-task Operating System: This is an operating system designed for multiple users at a time, allowing each to engage the computer at a real time and also make it possible for the computer to carry out several task. Examples of these operating system are: (i) A/AU (ii) CP/M (iii) Mac Os
  2. Network Operating System (NOS): This is a type of operating system that supports networking. Typically, a network operating system is located on a server and controls other computers and devices connected to the server.

The main difference between multi-user/multi task operating system and network operating system is that in network operating system, all computers are linked to a central server through the NOS. common examples are NT server, windows 2000 server, solaria Unix, Xerix, Novell’s network.

Other classification of operating system: Operating system can also be classified based on their interfaces using this criteria, we have.

  • Command-line Operating System (CL)
  • Graphical-User Interface (GUI) Operating System

(i) Command – line Operating System: There make use of commands usually typed on a line at a prompt. Examples are MS – DOS, Pc-Dos, UNIX, etc.

(ii) Graphical User Interface (OS): These are operating systems that contain commands and applications arranged in graphical forms and icons on the screen. They make computer technology more accessible, and are widely used in personal computers.

They allow users to enter commands with a point – and – click device, such as mouse instead of keyboard.


However, GUI system have the disadvantage of requiring more hardware – such as faster CPUs, more memory, and higher – quality monitors – then command – oriented operation system. Examples are MS – Windows, Linux, Mac Os, etc.


1) MS – DOS: This is an operating system designed for X86-based personal computer. It was the most commonly systems. It stands for Microsoft Disk Operating System.

The IBM – PC compatible computer of 1980’s till mid 1990’s made use of MS – DOS. To operate on MS – DOS, DOS commands are used. These commands can be internal commands or external commands. The internal commands are loaded into the computer memory during booting, while the external commands are usually contained in external storage and are only loaded when needed.

Examples of DOS commands are DIR, MD, CD, RD, CLS, COPY, TYPE, DEL, ERASE, TIME, DATE, etc.

2) UNIX: This is an operating system developed in 1969 by a group of At & T employees at Bell’s lab. It was first developed in assembly language but by 1973 had been almost entirely recorded in C language.

Originally, UNIX was meant to be a programmer workbench more than to be used to run application software. It was made to be freely distributed to government and academic institutions which led to being ported to a wider variety of machine families than any other operating system.

3) Microsoft Windows: These are series of operating systems and graphical user interface provided by Microsoft Windows was introduced as an add-on to MS – DOS in 1985 in response to the growing interest in graphical user interface. It is an operating system that allows users to manipulate small pictures, called icons on the computer screen to issue commands. It is the most widely operating system in the world.

Versions of Windows include Windows 2.0, Windows 3.0, Windows NT, Windows 98, Windows 2000, Windows ME, Windows Vista, Windows 7, Windows 8, Windows 10, etc.

4) Xenix: This is a multi-user, multi-tasking operating system developed by Microsoft. It can be said to be a Microsoft version of UNIX and mainly used in network environment because of its powerful security features.

5) Solaris: It is a version of UNIX developed by SUN Microsystem. It is a networking operating system designed mainly for E-commerce.

6) Embedded system operating systems: Mobile devices such as notebooks, smart phones, black berries, palm pilots etc. also have operating system. Some of these devices use proprietary operating system that is unique to the device while others use operating system such as Windows CE, Windows mobile, Android, Linux or other operating systems.

Embedded system operating systems are operating systems designed to operate on small devices such as Personal Digital Assistant (PDAs) or autonomous electronic devices such as robots, spetial probes and on-board vehicle computers. The main attribute of embedded system is their energy management and minimal resource ability.

Also See:

Computer Software




Computer Processing Devices

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