Function of Operating System

2. Main process management:

· Memory is organised as a large array of words or bytes that stores the user progarms and instructions for execution.

· The main memory is usually shared by OS and application programs. The memory manager keeps track of area of main memory where OS resides and where application programs reside.

· The memory manager also implement also implement various protection techniqes in order to protect the allocated memory from unauthorized access.

3. Secondary storage management:

· The main memory has a limited size and cannot store all the user programs at once. Moreover, when the power is lost the data it holds are also lost .so computer sustem provides secondary storage devices such as magnetic daisk and taps to back up main memory

· The secondary storage devices store system program, such as copiler,editor and assembler and user program that are not used frequently.

· The operating system performs following function in connection with disk management:

1. Free space management i:e., manages free spase on disk by reclaiming memory from used objects.

2. Storage allocation i:e., allocates storage area for storing new programs.

3. Disk scheduling.

4. File management:

· File is a storage unit and is a collection of information.

· Files are categorized on the basis of information stored in it such as data file, source file and object file.

· The operating system performance following function in connection with file management:

1. Creating and deleting files.

2. Creating and deleting directories.

3. Providing operations for manipulating files and directories such as read, write, execute, copy, appends etc.

4. Mapping the files onto secondary storage devices such as disk.

5. Backing up files on stable storage media so that they can be restoed if original is loss.

6. Input/output management:

· I/O devices attached to the computer system are used enter the data into the system and get the output.

· This subsystem manages all the I/O devices and cantain a variety of software program to handle these devices.

· Thus, devices management subsystem performs following tasks:

1. keep track of resources .this component of I/O subsystems is called I/O traffic controller.

2. reclaim the resource. However ,in most cases the I/O terminates auomatically.

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