Operating system is nothing but integral software which is intentionally designed to manage data & process flow between hardware & software. Here, software can be any user defined programs, applications, games, etc. All these applications could not run if only OS is absent. OS is the abbreviation of the operating system, which is most familiar in todays world.
Operating system offers numerous services for memory or RAM, which in turn processed at CPU. However various processes in between them are solely handled at operating system. This is very important layer between computer systems.
Many applications access information through application programming interface. This API is also called as system function call. OS refers to these calls through various interrupts & exception handling mechanism.
OS therefore acts as an interface between computer hardware & user application or program. Interrupts are the way with which processor interacts with external hardware, peripherals & different components of the OS.
Among other things, a multiprogramming operating system kernel must be responsible for managing all system memory which is currently in use by programs. This ensures that a program does not interfere with memory already used by another program.
Since programs time share, each program must have independent access to memory. Cooperative memory management, used by many early operating systems assumes that all programs make voluntary use of the kernels memory manager, and do not exceed their allocated memory.
This system of memory management is almost never seen anymore, since programs often contain bugs which can cause them to exceed their allocated memory.
If a program fails it may cause memory used by one or more other programs to be affected or overwritten. Malicious programs or viruses may purposefully alter another programs memory or may affect the operation of the operating system itself.
OS provides one of the important functionality called as crash management technique, which in turn handed over to CPU. In crash management, OS check for all predictable exception that is having possibility occur in future & provides perfect management functions for them.
Virtual memory is one of the demanding features of todays OS. It manages memory for larger program size. Therefore, it is possible to execute those programs having larger size than program memory & hardware. Virtual memory creates space in hard drive for such programs so that they would execute.
In multitasking, many program executions are handled simultaneously. It is not possible task in single tasking system like DOS.
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