13-04-2010, 11:22 PM
In computing, an operating system (OS) is software (programs and data) that provides an interface between the hardware and other software.s responsible for management and coordination of processes and allocation and sharing of hardware resources. It also acts as a host for computing applications running. An operating system may also provide orderly accesses to the hardware by competing software routines which relieves the application programmers . Applications access the services provided by the Operating systems through application programming interfaces (APIs) or system calls.
Features:
Program execution:
The operating system acts as an interface between an application and the hardware. The kernel creates a process by assigning memory and other resources.
Interrupts:
They provide an efficient way for the operating system to interact with and react to its environment.Interrupt-based programming is directly supported by most modern CPUs.
Protected mode and supervisor mode:
CPUs with dual mode operation capability use two modes: protected mode and supervisor mode, which allow certain CPU functions to be controlled and affected only by the operating system kernel. The protected mode refer to all modes which limit the capabilities of programs running in that mode, providing things like virtual memory addressing and limiting access to hardware in a manner determined by a program running in supervisor mode.
Memory management:
operating system kernel must be responsible for managing all system memory. Since programs time share, each program must have independent access to memory.Memory protection enables the kernel to limit a process' access to the computer's memory.part of the hard disk is reserved for virtual memory called as swap space.
An exhaustive information can be available at:
http://en.wikipediawiki/Operating_system
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visit this links for ppt:
http://web.cs.wpi.edu/~jb/CS502/lectures...erview.ppt
http://sethiclasses/cet421/daily_lecture_notes/chapter_02.ppt