A multi-user operating system is a computer operating system (OS) that allows multiple users on different computers or terminals to access a single system with one OS on it. These programs are often quite complicated and must be able to properly manage the necessary tasks required by the different users connected to it. The users will typically be at terminals or computers that give them access to the system through a network, as well as other machines on the system such as printers. A multi-user operating system differs from a single-user system on a network in that each user is accessing the same OS at different machines.
The operating system on a computer is one of the most important programs used. It is typically responsible for managing memory and processing for other applications and programs being run, as well as recognizing and using hardware connected to the system, and properly handling user interaction and data requests. On a system using a multi-user operating system this can be even more important, since multiple people require the system to be functioning properly simultaneously. This type of system is often used on mainframes and similar machines, and if the system fails it can affect dozens or even hundreds of people.
A multi-user operating system allows multiple users to access the data and processes of a single machine from different computers or terminals. These were previously often connected to the larger system through a wired network, though now wireless networking for this type of system is more common. A multi-user operating system is often used in businesses and offices where different users need to access the same resources, but these resources cannot be installed on every system. In a multi-user operating system, the OS must be able to handle the various needs and requests of all of the users effectively.
This means keeping the usage of resources appropriate for each user and keeping these resource allocations separate. By doing this, the multi-user operating system is able to better ensure that each user does not hinder the efforts of another, and that if the system fails or has an error for one user, it might not affect all of the other users. This makes a multi-user operating system typically quite a bit more complicated than a single-user system that only needs to handle the requests and operations of one person.
In a multi-user system, for example, the OS may need to handle numerous people attempting to use a single printer simultaneously. The system processes the requests and places the print jobs in a queue that keeps them organized and allows each job to print out one at a time. Without a multi-user OS, the jobs could become intermingled and the resulting printed pages would be virtually incomprehensible.
Source: WiseGeek