Operating Systems that run on desktop computers are the least powerful and least secure operating system. They are also the most familiar. Most of the people like to use Windows in their computer. They are very popular and easy to use. Three common types of operating systems are:

• Windows
• Apple’s System 8, or
• Rapidly fading DOS.

Operating System for Servers: Currently, computers in networks are connected to one another not directly but through powerful computers called services that provide security to the networks and route traffic from one network to another. These complicated tasks require special operating systems. These powerful operating systems are also used for tasks (such as engineering design, order processing, and payroll) critical to a company’s continued existence, called mission critical applications. Such tasks were previously run only on target mainframe computers. These powerful 32- or 64-bit operating systems are secure, multitasking, multithreading, and open. All now processes graphical user interfaces developed for then. All but OS/2 are portable in that they run on more than one type of microprocessor.

• Windows NT (NT stands for New Technology) is the fasted-growing server operating system. The upgraded version of NT is called Windows 2000.

• OS/2 (Operating System/2) competes with windows and is a powerful operating system but has had trouble catching on.

• UNIX a powerful operating system for server was originally developed at AT&T’s Bell Labs in 1973.

Operating Systems for Mainfarame: In the early days of computer, mainframe and minicomputers dominated the computing world, and each computer company developed its own operating system. For example, some IBM mainframe computers use an operating system called open VMS and Digital Equipment Corporation minicomputers use one called VMS. These companies developed not just their own operating systems but also the applications that ran on top of them. These are called proprietary system because they are all owned by a single proprietor. Because there were so many competing operating systems, it was hard to make computers talk to one another. Although costly, these operating systems are both powerful and secure and capable of handling a variety of tasks.

Handheld operating systems: Windows CE, visually similar to Windows 95, uses a small keyboard and a touch-sensitive screen.

Embedded operating systems: Generally, a microprocessor is used inside a small device such as a watch, and it needs an operating system. Such an operating system is stored in a memory chip instead of a hard drive and turns on instantly when the device is turned on.