Operating system is the software that performs all the basic tasks of a computer system. It works like an interface between user and computer hardware resources. It actually controls the execution of all the tasks that are performed in a computer. Some examples of operating systems are Unix, MS-DOS, Windows 98/2000/XP.
It enables a user to utilise hardware resources very efficiently. So, operating system makes it easy for a user to use computer system.
“An operating system is a collection of programs that controls and coordinates all the tasks and functions in a computer system and mediates between application programs and the hardware components.”
Basics of Operating System
Operating system is the main part of the system software of any computer. It mainly provides an environment to run the software and provides services to the computer hardware. Basically operating system has two main objectives:
(i) Managing the computer’s hardware
(ii) Providing the interface
Functions of Operating System
The main functions of an operating system are as follows:
(i) Process Management When two or more jobs are in a queue (to be processed), operating system decides which one of them will get the attention of CPU. It is very important task as various programs and input methods compete for the attention of CPU and demand memory, storage, resources, etc, for their own purposes.
(ii) Memory Management As a memory manager, the operating system handles the allocation and deallocation of memory space as required by various programs.
(iii) File Management The operating system is responsible for creation and deletion of files and directories. It also takes care of other file related activities such as organising, storing, retrieving, naming and protecting the files.
(iv) Device Management Operating system provides input/output sub system between processes and device drivers. It handles the device caches, buffers and interrupts. It also detects the device failures and notifies the same to the user.
(v) Security Management The operating system protects system resources and information against destruction and unauthourised use, it keeps different program and data in such a manner that they do not interfere with each other.
(vi) User Interface Operating system provides interface between user and hardware. User interface is a layer that actually interacts with the computer operator. The interface consists of a set of commands or menus through which a user communicates with a program.
Basics of Popular Operating System
Now-a-days, various operating systems are available in market and being used in various computers but most widely used are Linux and Windows.
Linux is an open source computer operating system designed primarily for the PCs. Linux was designed considering Unix compatibility. It’s functionality list is quite similar to that of Unix. One of the most valued advantage of Linux over the other platforms lies with the high security levels it ensures (It is a virus free operating system).
Elements of Linux
The basic elements of Linux are described as:
(i) Kernel It is a core component of Linux and provides basic services for all other parts of the operating system.
(ii) Shell It is a program that provides interface between user and kernel. It is used for executing the commands. It is also called command interpreter. It also provides a special interpreter program which can be used to execute commands of the operating system. It can be used to do various types of operations, call application program etc.
(iii) File System Linux treats everything as a file. Even a directory is treated as a file. File system is a logical way to describe the collection of storage available to the computer. In linux, file system mostly based on hierarchical structure. The upper most directory is known as root directory. It is expressed with a slash (/). All the files and directories are connected to root directory.
Terminology related to file system are:
(a) Partition of a disk is a logical division of the collection of storage devices into independent units.
(b) Directory is a user specified location that allows user to organise files.
(c) File is the basic unit of storage in the logical file system.
(d) Path is a description of how to reach a particular file or directory.
(e) Inode is a data structure stored in the file system that identifies the file and its attributes.
(f) Link is a combination of a file’s name and the inode number that represent the file.
Hierarchical File System
A hierarchical file system is one that contains directories and sub-directories. Figure shows the lists standard system directories in Linux. Linux supports MS-DOS, MINIX, ISO 9660, VFAT, etc.