Linux is Multiuser, Multitasking Operating System HOW ?

A single user operating system provides the facilities to be used on one computer by only one user. In other words, it supports one user at a time. However, it may support more than one profile. Single keyboard and single monitor are used for the purpose of interaction. The most common example of a single user operating system is a system that is found in a typical home computer.

There are two general types of single-user operating system:

1. Single tasking

2. Multitasking systems

Single tasking systems are the systems which are designed to manage the computer so that one user can effectively do one thing at a time.

The Palm OS for Palm hand held computers is a good example of a modern single-user, 
single-task operating system. DOS is also one the examples.

Multitasking operating system allows more than one program to be running at the same time, from the point of view of human time scales. A single-tasking system has only one running program. 

Multi-tasking can be of two types: 

1. Pre-emptive

2. Co-operative 

In pre-emptive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs. Unix-like operating systems such as Solaris and Linux support pre-emptive multitasking.

 Cooperative multitasking is achieved by relying on each process to give time to the other processes in a defined manner.

Multi-user

A multi-user operating system allows multiple users to access a computer system at the same time. Time-sharing systems and Internet servers can be classified as multi-user systems as they enable multiple-user access to a computer through the sharing of time. Single-user operating systems have only one user but may allow multiple programs to run at the same time.

Linux, UNIX, VMS and mainframe operating systems.