Operating system The most fundamental software run on a computer. All computers have an operating system, which is used among other things to start and run other programs. The operating system performs important tasks, such as receiving data from the keyboard and mouse, sending data to the screen, keeping files and folders under control and checking the various units in the machine (e.g. disks, printers etc). An operating system as a rule also contains a user interface, which for example enables the user to control the machine using graphic icons, windows and menus.

Open source first evolved during the 1970s. Richard Stallman, an American software developer who believes that Sharing source-code and ideas are fundamental to freedom of speech, developed a ‘free’ version of the widely used ‘Unix’ operating system. The resulting ‘GNU’ program was released under a specially created General Public License (‘GNU GPL’). This was designed to ensure that the source-code would remain openly available to all. It was not intended to prevent commercial usage or distribution.

System calls provide the interface between a running program and the operating system. These calls are generally available as assembly- language instructions, and are usually listed in the manuals used by assembly-language programmers.

Some systems may allow system calls to be made directly from a higher-level language programm in which case the calls normally resemble predefined function or subroutine calls. They may generate a call to a special run-time routine that makes the system call, or the system call may be generated directly in-line.

During lifetime of process,it go through varius states of operations which are called mode or state of process.a operating system process can be in one of following state at a time:-

Process management is one of the most important and relevant tasks in operating syste.

Process:-In operating systems, process is defined as “A program in execution”.Process can be considered as an entity that consists of a number of elements, including: identifier, state, priority, program counter, memory pointer, context data, and I/O request.Components of process are:-

Operating system is a collection of software programs and it is responsible for the management and coordination of activities and the sharing of the limited resources of the computer.The operating system acts as an interface between an application and the hardware.The operating system is a set of services which simplifies development of applications. Executing a program involves the creation of a process by the operating system.

• Memory Management
• File organization
• Disk Space Management
• Process Management
• User Management
• Security And Network