Multi-Tasking

This term describes an Operating System that can perform several tasks simultaneously. For example, on your computer you may browse the web, print a document, and perform several other tasks, all at once. Most computers only have one processor, so they perform multi-tasking by giving each task a short time on the processor in turn. Some computer have more than one processor, so can genuinely perform more than one task at time.

Multi-User

This term describes an Operating System that can have two or more concurrent users. Each one has their own 'space' within the operating system. For an individual user, it may appear that they are the only one using the operating system, even though there may be many others using it at the same time.

Operating System

An operating system is a piece of software. Its task is to manage the hardware resources of your computer, and make them available for useful tasks. Examples of tasks performed by an operating system are:

• Keep track of the memory and disk space in the computer. Keep a list of where everything is stored. If a user or another piece of software requests some memory or disk space, allocate some to it.
• Manage the main processor in the computer. If more than one task is running on the computer, make sure they all have access to the processor on a fair basis.
• Manage other hardware devices. For example, if the computer has a modem attached, the operating system keeps track of whether or not anyone is using it, and prevents more than one task from using it at a time.

UNIX^®, Microsoft Windows, and MacOS are all different types of operating systems, and there are many others.

Single User

This term describes an Operating System that can be used by only one user at a time. Although the computer may be used by more than one person, they can not use it concurrently. Note that a single user operating system can still be multi-tasking.