Operating Systems

Operating systems

The operating system is a program or set of programs that manages the operation of the computer for the user. It acts as a bridge between the user and the computer hardware; this essential  since the user cannot communicate with hardware directly.

The OS is held in permanent storage, for example on the hard disk. A small program called the loader is held in ROM (read only memory). When a computer is switched on, the loader in ROM sends instructions to the load the operating system by copying it from storage into RAM (Random Access Memory). 

Functions of an operating system

The operating system enables the user to complete all their various tasks such as loading and running programs or apps, saving or printing files. It provides a simple interface to enable the user to give instructions.

Types of operating system

Single-user, single task

The OS could only load and run one program at a time. The most likely place to find such an operating system would be embedded in a device such as a digital camera. 

The OS typically has a menu interface to enable the user to select settings, and button and other controls to operate the camera. It is single-task in that, even though it can perform many different tasks, it cannot do more than one thing at a time. 

Single-user, multi-task 

This is the type of OS which runs on a stand alone PC or laptop. The windows OS, for example, can run many jobs simultaneously, switching rapidly between them so that each one appears to be the only one running. 

You can, for example, be playing music, editing a word document and checking your emails occasionally. 

Types of OS: multi-user

Time-sharing systems are multi-user, multi-tasking systems. A single powerful mainframe or supercomputer may be connected to hundreds of terminals all using the mainframe CPU. Each user gets a slice of processor time according to a scheduling algorithm. Very large organisations such as banks and credit card companies which process huge numbers of transactions use mainframes. 

The role of the operating system

• Managing networks

  • A network OS may be based on a client-server network in which a server enables multiple clients to share resources. Programs and data may be held in a dedicated file server, enabling all client devices clients to share resources.

• …