An operating system acts as an intermediary between the user of a computer and the computer hardware. The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner.
An operating system is a software that manages the computer hardware. The hardware must provide appropriate mechanisms to ensure the correct operation of the computer system and to prevent user programs from interfering with the proper operation of the system.
Mainframe operating systems are designed primarily to optimize utilization of hardware. Some operating systems are designed to be convenient, others to be efficient, and others to be a combination of the two. An operating system is complex, It must be created piece by piece. Each of these pieces must be a well-delineated portion of the system, with carefully defined inputs, outputs and functions.
A computer program can be roughly divided into four components
- The hardware.
- The operating system.
- The Application Programs.
- The users.
An operating system is like a government. Like a government does no useful function by itself, It just provides an environment within which other programs can do useful work. To understand more fully a operating system’s role, We need to explore operating systems from two viewpoints: that of the user and that of the system.
The user’s view of the computer varies according to the interface being used. Most computer users sit in front of a PC, consisting of a monitor, keyboard, mouse and system unit. Such a system is designed for one user to monopolize its resources. The goal is to maximize the work that the user is performing. In this case.
In this case, the operating system is designed mostly for ease of use, with some attention paid to performance and none paid to resource utilization. Performance is of course important to the user, but such systems are optimized for the single-user experience rather than the requirements of multiple users. In other cases, a user sits at the terminal connected to a mainframe or a minicomputer. Other users are accessing the same computer through the terminals. Other users share resources and may exchange information. The operating system in such cases is designed to maximise resource utilization. This is done to assure that no individual user takes more than her fair share.
In other cases, users sit at workstations connected to networks of other workstations and servers. These users have dedicated resources at their disposal, but they also share resources such as networking and servers, for example, Printers. Therefore their operating system is designed to compromise between individual usability and resource utilization.
Some computers have little or no user view. For example, embedded computers in household devices have little or no user view. and automobiles may have numeric keypads and may turn on indicator lights on or off to show status, but they and their operating systems are designed primarily to run without user intervention.
From the computer’s point of view, the operating system is the program most intimately involved with the hardware. In this context, we can view an operating system as a resource allocator. A computer system has many resources that may be required to solve a problem. For example, CPU, Memory Space, File storage place, The operating system acts as the manager of these resources. Facing numerous and possibly conflicting requests for resources, the operating system must decide how to allocate them to specific programs and users so that it can operate the computer system efficiently and fairly. As we have seen before that resource allocation is especially important when there are many users accessing the same mainframe or minicomputer.
How are operating systems defined?
An operating system is a control program. A control program manages the execution of user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of Input Output devices.
In the above paragraphs we had a look at the operating system from the perspective of the user and that of the system. However how can we define an operating system in general? We talked about many different definitions of operating systems above but we don’t have any completely adequate definition of an operating system. Operating systems exist because they offer a reasonable way to solve the problem of creating a usable computing system.
The fundamental goal of computer systems is to execute user programs and to make solving user’s problems in a easier way. Towards this goal, computer hardware is constructed, Since bare hardware alone is not particularly easy to use, application programs are developed. These programs require certain common operations, such as those controlling input output devices. The common functions of controlling and allocating resources are then brought together into one piece of software: the operating system.
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