Main Functions of an Operating System

A separate module of operating system software performs following functions:

• Process Management: A process is a program in execution. During execution a process needs certain resources such as CPU time, memory space and I/O devices. At a particular instance of time, a computer system normally consists of a collection of processes. Process management module take care of creation and deletion of processes, scheduling of system resources to different processes requesting them and providing mechanisms for synchronization and communication among processes.
• Memory Management: To execute a program, it must be loaded in main memory (at least partially) together with the data it accesses. To improve CPU utilization and to provide better response time to its users, a computer system normally keeps several programs in main memory. Memory management module takes care of allocation and de-allocation of memory space to programs in need of  this resource.
• File Management: All computer systems store, retrieve and share information. Normally, a computer stores such information in units called files. Process read information from files and create new files for storing newly generated information. File management modules takes care of file related activities such as organization, storage, retrieval, naming, sharing and protection of files.
• Device Management: Normally, a computer system consists of several I/O devices such as terminal printer, disk and tape. The device management module of an operating system controls all I\O devices. It keeps track of I\O requests from processes, issues commands as I\O devices and ensures correct data transmission to\from an I\O device. It also provides a simple and easy interface between the devices and rest of the system.
• Security: Computer systems often store large amount of information, some of which are highly sensitive and valuable for its users. Users can trust a computer system and rely on it only if its various resources and information stored in it are protected against destruction and unauthorized access. Security modules protects the resources and information of a computer system against destruction and unauthorized access. It also ensures that when the system executes several disjoint processes simultaneously, one process does not interfere with others or with the operating system itself.
• Command Interpretation: Command interpretation module interprets user commands and directs system resources to process the commands.