List the typical functions of operating systems.
Classical functions of operating system are given as:
(1) Process management: A process is a program throughout execution. This is the job that is currently being executed through the processor. In its execution a process would need certain system resources as processor, time, main memory and files etc. Operating system supports many processes concurrently. The process management module of the operating system takes care of the creation and termination of the processes, allocating resources to the processes, scheduling processor time to various processes and communication among processes.
(2) Memory management module: This takes care of the allocation and de-allocation of the main memory to the different processes. It also allocates main and secondary memory to the system or user program and data. To execute a program, binary image of it, should be loaded into the main memory.
Operating System decides:
(a) A part of memory are being currently utilized and by whom.
(b) Which one process to must be allocated memory.
(c) Allocation and de-allocation of memory space.
(3) Input/outputs management: such type module of the operating system co-ordinates and assigns various I/O devices namely printers, terminals, disk drives and tape drives etc. This controls all I/O devices, continues track of I/O request, issues command to such devices.
I/O subsystem consists of:
(i) Memory management component which includes buffering, caching and spooling.
(ii) Device driver interface
(iii) Device drivers exact to hardware devices.
(4) File management: Data is stored in a computer system as files. Such module of the operating system would handle files held on various storage devices and transfer of files from one device to the other. This module takes care of creation, organization, naming, storage, sharing, back-up and protection of various files.
(5) Scheduling: The operating system also establishes and enforces process priority. It is determines and preserves the order wherein the jobs are to be executed through the computer system. It is so because the most significant job must be executed initially followed through less important jobs.
(6) Security management: This module of the OS ensures data security and integrity. It protects data and program from destruction and unauthorized access. This keeps different programs and data which are executing concurrently into the memory in such a way which they do not interfere along with each other.
(7) Processor management: Operating system assigns processor to the different task that should be performed through the computer system. If the computer has more than one processor idle, one of the processes waiting to be executed is allocated to the idle processor.
OS keeps internal time clock and log of system usage for all the users. This also creates error message and their debugging and error detecting codes for correcting programs.