Operating System The system software that manages computer hardware, software resources and provides common services for computer programs. ...

Operating System

The system software that manages computer hardware, software resources and provides common services for computer programs. It acts as interface between computer hardware components and the user.

Functions of an OS

1. I/O management:

In computing, input/output management refers to the transformation of data between input and output devices of the computer system. A request for I/O from a user process is signaled to the operating system using a system call. 

OS accepts the input from the input device, stores it in the main memory, ask the CPU to process it and finally provides the result to the output devices.

2. Data management: 

OS govern the input and output of data and their location, storage, and retrieval. It is responsible for storing and retrieving information on disk drives and for the organization of that information on the drive.

3. Memory management: 

When the user requests CPU for read/write operation, OS determines the amount of required memory to load the program and data into RAM or main memory. When the program terminates, its memory space will be free and the same memory area or address can be allocated to other new programs.

4. Process management: 

OS decides the order in which processes have access to the processor, and how much processing time each process has. It finds the status of processors and processes, chooses a job, chooses process in the job, allocates the processor to the process and frees the processor when the process is executed.

5. Device management: 

OS manages all device communication using their respective device-drivers. It finds the status of device, channels and control units. It also allocates devices in an effective and efficient way and de-allocates devices when they are no longer required.

6. File management: 

OS manages files with their different extensions into directories for efficient and usage in the computer system. It helps to create new files and placing them at specific locations in the computer system. It helps in easily and quickly locating these files.

7. Security management: 

The security management refers to provide protection of resources such as CPU, memory, disk, software programs, and most importantly data or information stored in the computer system. It is one of the topmost functions and responsibility of OS to create a protection of hardware and software systems.

8. Virtual Storage: 

The OS uses free space of secondary memory such as hard disk which is termed as virtual memory. Only those pages, which are required at a particular time, are kept in the main memory. The area of secondary storage used for storing pages is called virtual storage.

9. Command Interpreter:

10. Time sharing: 

11. Deadlock prevention: 

12.Interrupt handling: 

Types of OS

• Single user, single tasking
• Single user, multi tasking
• Multi user, multi tasking
• Real Time Operating System (RTOS)

1. Single user, single tasking

This type of operating system manages the computer so that one user can effectively do one thing at a time. Functions like printing a document, downloading images, etc., can be performed only one at a time.

Eg: MS Dos, Palm OS

2. Single user, multi tasking

An operating system that allows a single user to perform more than one task at a time is called Single-User Multitasking Operating System. This is the type of OS most desktops and laptops use today.

Examples include Microsoft Windows and Macintosh OS

3. Multi user, multi tasking

This type of operating system allows two or more users to run programs at the same time. It is an operating system that permits several users to utilize the programs that are concurrently running on a single network server. The single network server is termed as "Terminal server". "Terminal client" is a software that supports user sessions.

Eg: Linux, Unix, Mainframe OS, Ubuntu

4. Real Time Operating System (RTOS)

RTOS are used to control machinery scientific instruments and industrial system. Real-time operating system is designed to run real-time applications. It can be both single- and multi-tasking.

Eg: PSOS, VRTX, RT Linux, Lynx  etc

Classification of OS based on User Interface

• Graphical User Interface (GUI)
• Character User Interface (CUI)

1. Graphical User Interface

A graphical user interface allows the user to enter commands by pointing and clicking at objects that appear on the screen. It is a human-computer interface that uses windows, icons and menus and which can be manipulated by a mouse.

2. Chatacter User Interface

Character User Interface is a mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks.

Difference between GUI and CUI

S.N	Graphical User Interface (GUI)	S.N	Character User Interface (CUI)
1.	GUI is easy to operate and user friendly.	1.	CUI is less user-friendly than GUI.
2.	It can display graphics, icons, pictures, multimedia etc	2.	It cannot display graphics, icons, pictures, multimedia etc
3.	Users do not need to remember all the commands.	3.	Users have to remember all the commands.
4.	It requires a larger memory space and faster processors to operate.	4.	It requires less memory and low processing speed computers.
5.	GUI based OS are usually 32 or 64 bit OSs.	5.	CUI based OS is usually 8 or 16 bit OS.

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