The operating system (English : the operating system ; OS ) is a set of programs that manage computer hardware resources or hardware , and provide common services for application software . The operating system is the most important type of system software in a computer system . Without the operating system , the user can not run an application program on their computer , unless the application program boot .
The operating system has a systematic scheduling includes memory usage calculation , data processing , data storage , and other resources .
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 , [ 1 ] [ 2 ] although the application code is usually executed directly by the hardware and will frequently call the OS or disconnected by it . Operating systems are found on almost any device that contains a computer - from mobile phones and video game consoles to supercomputers and web servers .
Examples of modern operating systems are Linux , Android , iOS , Mac OS X , and Microsoft Windows
Processor [edit | edit source ]
The processor executes computer programs . The processor is a chip in the computer system that runs the computer program instructions . In every second the processor can execute millions of instructions .
The program is a series of instructions given to a computer . While the process is a part of the program that are in a particular status in the execution sequence . In the discussion Operating Systems , we often discuss the process compared with the program . In a modern operating system , in particular when not all programs loaded in memory , but only one part of the program . While other parts of the program remains rest in the disk storage media . Only in times of need alone , part of the program loaded in the memory and executable by the processor . This greatly saves memory consumption .
Some systems run only a single process at a time , while others run a multi - process at a time . Though most of the computer system has only one processor , and a processor can execute only one instruction at a time . So how a single processor system can run multi - process ? Surely, in a very small granularity , the processor executes only one process at a time , then quickly he moved to run other processes , and so on . So for vision and feeling of a human user , as if the processor run multiple processes simultaneously .
Each process in an operating system to get a PCB ( Process Control Block ) which contains information about the process , namely : an identification process ( Process ID ) a unique identity and become the number , the status of the process , the process execution priorities and process location information in memory . Priority process is a value or quantity that indicates how often the process should be executed by the processor . The process that has a higher priority , be executed or executed more often than the first lower -priority processes . An operating system can only specify all processes with the same priority , so that each process has an equal opportunity . An operating system can also change the priority value of a particular process , so the process will be able to have a greater chance at the next execution ( for example : on a process that was already too long waiting for execution , the operating system raises the value priorities ) .
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