Operating System
Sunday, October 17, 2010|
adminWhat is Operating System?
An operating system (OS) is software, consisting of programs and data, that runs on computers and manages the computer hardware and provides common services for efficient execution of various application software.Operating System is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs.
For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between application programs and the computer hardware,although the application code is usually executed directly by the hardware, but will frequently call the OS or be interrupted by it. Operating systems are found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.
Operating systems can be classified as:
- multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.A multiuser operating system enables multiple users to run programs simultaneously. This type of operating system may be used for just a few people or hundreds of them. In fact, there are some operating systems that are used to allow thousands of people to run programs at the same time.
- multiprocessing : Supports running a program on more than one CPU.A multiprocessing operating system allows a program to run on more than one central processing unit (CPU) at a time. This can come in very handy in some work environments, at schools, and even for some home-computing situations.
- multitasking : Allows more than one program to run concurrently.Multitasking operating systems work a little differently; they make it possible to run more than one program at a time.
- multithreading : Allows different parts of a single program to run concurrently.Multithreading operating systems are even more different, allowing varied parts of one program to be used simultaneously
- real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.Real-time operating systems are designed to allow computers to process and respond to input instantly. Usually, general-purpose operating systems, such as disk operating system (DOS), are not considered real time, as they may require seconds or minutes to respond to input. Real-time operating systems are typically used when computers must react to the consistent input of information without delay.
In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer and would arrive at a scheduled time with program and data on punched paper cards and tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a front panel using toggle switches and panel lights. It is said that Alan Turing was a master of this on the early Manchester Mark 1 machine, and he was already deriving the primitive conception of an operating system from the principles of the Universal Turing machine.
Later machines came with libraries of software, which would be linked to a user's program to assist in operations such as input and output and generating computer code from human-readable symbolic code. This was the genesis of the modern-day operating system. However, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a washing line from which tapes were hung with different colored clothes-pegs to indicate job-priority.
Examples of Operating System
Posted in
sofware
0 comments for this post
Leave a reply