What are the various components of an Operating System (OS)?

System Components:

 

Every operating system consists of following system components viz.

 

1.    Process management

2.    Main memory management

3.    File management

4.    Secondary storage management

5.    IO system management

6.    Networking

7.    Protection system

8.    Command interpreter system

 

1.     Process Management:

A process refers to a program in execution. The process abstraction is a fundamental OS mechanism to manage concurrent program execution.  The OS responds by creating a process. A process needs certain resources such as CPU time, memory, files and IO devices.  These resources are either given to the process when it is created or allocated to it while it is running.

 

When the process terminates the operating system will reclaim any reusable resources. The term process refers to an executing set of machine instructions.  A program by itself is not a process.  A program is a passive entity while a process is an active entity. The operating system is responsible for the following activities of the process management:

• Creating and destroying of the user and system processes.
• Allocation of hardware resources among the processes.
• Controlling the progress of processes.
• Providing mechanisms for a process communications.
• To provide mechanism for deadlock handling.

 

2.     Main Memory Management:

Memory management module of an OS is concerned with the management of primary memory.  Memory management is concerned with the following functions:

• Keeping track of the status of each location of main memory i.e. each memory location is either free or allocated.
• Determining allocation policy for memory.
• Allocation technique i.e. particular location must be selected and allocation information updated.
• De-allocation technique and policy.  After de-allocation, status information must be updated.

Memory management is primarily concerned with allocation of physical memory of finite capacity to requesting processes.  Overall resource utilization and other performance criteria of a computer system are affected by performance of the memory management module.  Many memory management schemes are available and the effectiveness of the different algorithms depends on the particular situation.

 

3.     File Management:

File is a named, logical collection of information on the secondary storage.  Computers use physical storage media for storing the different information. A file may contain report, an executable program or a set of commands to the OS.  A file consists of sequence of bits, bytes, lines or records whose meanings are defined by their creators.

For storing the files physical media is used. Physical media are of different types like a magnetic disk, magnetic tape and optical disk etc.  All the media has its own characteristics and physical organization.

 

 An OS is responsible for the following in connection with the file management:

• Creating and deleting of files
• Mapping files onto secondary storage
• Creating and deleting directories
• Backing up files on stable storage media
• Supporting primitives for manipulating files and directories
• Transmission of file elements between main and secondary storage

 

4.    Secondary Storage Management:

Secondary storage device is used for storing all the data and programs.  These programs and data access by computer system must be kept in main memory.  Size of main memory is small to accommodate all data and programs.  It also loses the data when the power is lost.  For this reason secondary storage devices are used.  Therefore the proper management of disk storage is of central importance to a computer system.

 An OS is responsible for following activities related to disk management:

• Free space management
• Storage allocation
• Disk scheduling

 

5.     IO System Management:

The module that keeps track of the status of devices is called the IO traffic controller.  Each IO device has a device handler that resides in a separate process associated with that device.

 

The IO subsystem consists of:

1. A memory management component that includes buffering, caching and spooling.
2. A general device driver interface.
3. Drivers for specific hardware devices.

 

6.     Networking:

It enables computer users to share resources and speed up computation. The processes communicate with one another through various communication lines.

 

Following parameters are considered while designing the networks:

• Topology of network
• Type of network
• Physical media
• Communication protocols
• Routing algorithm

 

7.     Protection System:

Modern computer systems support many users and allow the concurrent execution of multiple processes.  Organizations rely on computers to store information. The information and devices must be protected from unauthorized users or processes.  The protection is any mechanism for controlling the access of programs; processes or users to the resources defined by a computer system.

They are implemented in OS to support various security policies. The goal of the security system is to authenticate subjects and to authorize their access to any object. It can improve reliability by detecting latent errors at the interfaces between component subsystems. 

 

8.     Command Interpreter System:

It is an interface between user and the OS.  It is a system program for an operating system.  The command interpreter is a special program in a UNIX and MS DOS operating system. The command interpreter is included in the kernel of some OS. 

When users log in first time or when a job is initiated, a control statement is processed by the command interpreter. Command interpreter reads the control statements, analyses it and carries out the required action.