Single User Operating System
A single user operating system allows only one user to use it at a time. The users can protect their files with passwords and will ensure that they are able to carry out actions with the hardware and use the software that they want to.
The first attempt at improving the efficency of was to take away the slowest part of the process (the human being) and to use some other method to first collect all the input data. Once the data has been collected it could be input to the processor using the fastest input devices available. In this way one processor can be used to satisfy the demands of a number of users, although it may be some time before a response is produced as all the input data has to be collected before the processing is done. A good example is when workers input the times at which they start work and finish work each day during the week. This data is collected in some way and then input into the computer and only when all the data is collected it is used to calculate the pay for each worker for the week, The OS which insists on being collected together first and then input all together is called a Batch OS. Batch OSs where developed in the 1950s because there were very few computers but lots of people wanting to use them. The only way to satisfy demand was to stop people slowing the computer down.
Multi-User Operating System
Nowadays there us another reason for wanting to let lots of people all use the same computer at the same time. If a database of information needs to be stored centrally and accessed by many people then one way is to use a Multi-User OS. A good example of this would be a supermarket checkout system. All the checkouts need to have access to the same set of information: the stock file. The way it is done is that each of the tills (terminals) are given a little bit of time on the computer before it goes on and gives the next till a little bit of time. This can be repeated for however many tills there are before going back to the first one again. Remember that the computer processor is capable of very fast processing which allows it to do everything a till needs in about 1/100th of a second. This means that the human beings involved in the process do not notice and think that the terminal at the till is concentrating on their shopping all the time.
Networking and Distributed Systems
Another way of sharing the same information is to network a number of computers so that they can all share the same resources. This is probably the sort of system that you are taught on at school. When you switch your computer on and identify yourself the first thing that needs to happen is that software and data files need to be downloaded from a central resource onto your particular machine. After that your machine can work independently of the rest of the network because it is a computer unlike the terminals in a multi-user OS which all rely on one central computer for all their processing.