What are operating systems? Can be answered at several levels.
Firstly, an operating system is a program, or a set of programs. Operating systems vary in size from very small to very large, but all are pieces of software. In the past, almost all operating systems were written in a low level language. Currently, many operating systems are partly or completely written in a high level language.
Secondly, an operating system is by virtue of its name, a system. It is a collection of parts, working together towards some common goals. The goals or objectives of an operating system of the computer may be regarded as the manager of these resources.
Thirdly, a computer may be regarded as a set of devices, or resources, which provide a number of services, such as input, processing, storage and output. The operating system of the computer may be regarded as the manager of these resources. Lt controls the way in which these resources are put to work.
Finally, an operating system is the lowest layer of software on a computer. It acts directly on the “raw” hardware of the computer. It supports other layers of software such as compilers and applications programs. Part of the task of an operating system is to “cushion” users from the complexities of direct use of the computer hardware.
In summary, an operating system is a program, or set of programs driving the raw hardware of a computer, which manages the resources of the computer in accordance with certain objectives, providing higher layers of software with a simplified computer.
Operating systems are as old as electronic computers. It was realized from the start that the hardware of a computer of its own is very difficult to use. Various supervisor, executive or monitor programs were written to make aspects of causing a computer easier. As time went by, these programs became larger, more complex, and, unfortunately, slower, not very efficient and less reliable.
Today big operating systems face a new challenge, from cheap, plentiful microcomputer, which require only the simplest of monitor programs for their operation.