Classification of Operating Systems

Operating systems can be classified according to:

1. Number of tasks.
2. Number of users.
3. Human-computer interface (HCI).

Classification According to Tasks:

Single Program Operating System:

An operating system that allows a single user to perform only one task at a time is called a Single-User Single-Tasking Operating System. This essentially means that a user can only run one interactive program at a time. Functions like printing a document, downloading images, etc., cannot be performed at the same time.

The user must exit from the current program before loading and running another program. An example of a single-user operating system is MS-DOS.

Multitasking Operating System:

This type of operating system allows a single CPU to run many programs simultaneously (at the same time). Microsoft Windows 2000, IBM’s OS/390, and Linux are examples of operating systems that can do multitasking (almost all of today’s operating systems can).

Classification According to the Number of Users:

Single-user Operating System:

A single-user operating system is designed for use by only one person. It cannot support more than one person and runs only one user application at a time. MS-DOS is an example of a single-user operating system. Older versions of Windows like Windows 3x, Windows 95, 97, and 98 are other examples.

Multi-user Operating System:

Multi-user or multi-access operating system allows more than one user to interactively use the computer. It can be installed on a computer that is accessed by many people at the same time. Examples of such operating systems are UNIX, Novell and Windows NT/2000, Linux.

Classification According to Interface:

The term human-computer interface refers to the method of interaction between the computer and the user and determines how easily the user can operate the computer. The underlying principle in operating system design is to make complex tasks very simple for the user to carry out.

Currently, the three main types of human-computer interfaces are:

• Command Line Interface (CLI)
• Graphical User Interface (GUI)
• Menu Driven Interface (MDI)

Command Line Interface (CLI): The user interacts with a computer by typing a command at the prompt found on a command line.

Graphical User Interface (GUI): Graphical User Interface (GUI) is a digital interface in which a user interacts with graphical components such as icons, buttons, and menus.

Menu Driven Interface (MDI): The menu-driven interface employs a series of screens, or “menus”. When a user makes a selection by tapping/clicking on the list format or graphics, it takes them to the next menu screen until they complete the desired outcome.