Operating System
- An operating system is a software component of a computer and is responsible for the management of a variety of computer operations as also the sharing of computer resources.
- An operating system acts as an interface between the application programs and the computer hardware. Desktop computers, PDAs, laptop computers, notebook computers, and even most mobile phones of today, come with an operating system.
- It hosts computer applications and handles the operations of computer hardware.
Fundamentals
Access Control: When a computer is started, it runs in the supervisor mode, which means that the first few programs running on the computer and the operating system have unlimited access to the hardware. An operating system has the ability to place a computer in the protected mode, wherein programs are given limited access to computer resources.
Execution of Programs: Programs in execution are known as processes. The execution of a program requires the operating system to create processes. The operating system kernel creates a process by loading program code from the disk and allocating memory to it before running the program.
User Interface: Users interact with operating systems by means of command-line interfaces or graphical user interfaces. Though a graphical user interface cannot be referred to as an operating system service, many operating systems integrate support for user interfaces into their kernels.
Memory Management: The operating system kernel handles the allocation and management of memory that programs use. The operating system kernel controls the amount of memory allocated to application programs. An operating system can use the same memory locations for multiple tasks, using the underlying concept of virtual memory and swapping or paging.
Scheduling: An operating system kernel consists of a scheduler program that manages the time taken by each program for its execution. The kernel passes the controls to processes whereby they can access the CPU and memory.
Interrupt Handling: An operating system has to deal with unexpected events in program execution. They are known as interrupts. Interrupts may also come from the computer hardware. If a piece of computer hardware triggers an interrupt, the operating system kernel devises ways to handle it. Interrupts triggered by running programs can also be handled by the operating system kernel.
Management of Files: Operating systems are in charge of handling the application program access to files stored on the disk. File systems are methods used for storing and managing computer files and data. A file system can be considered as a specialized storage system for the organization, access, and retrieval of data.
Computer Security: It is a function of the operating system to handle multiple user profiles. When you log in to your user account on the operating system you use, you are actually being a part of the security measures implemented by your operating system.
Computer Networking: Operating systems support a variety of networking protocols, whereby computers running different operating systems can work over a common network. The operating system support for networking protocols enables the computers to access resources on remote computers in fairly simple ways.