Introduction to Operating Systems

An Operating System or OS is a collection of system program controls the operations of computer system. it activates and recognizes the hardware devices and provides the operating environment for other application software. It acts like the intermediary between a user and the computer hardware. Few examples of operating systems are UNIX, MS-DOS, MS-Windows, Linux etc.

OS has major two objectives.

1. Activate the hardware devises
2. Provide an interactive interface to the user and interpret commands so that it can communicate with the hardware.

Types of OS

There are many types of operating systems. We can categorize it according to the user involved to operate it like single user and multiuser operating system.

According to the processing we have single processing, multiprocessing operating system, real time system, batch processing system etc.

But in broad approach, we can classify the operating system on the basis user interface like command or character user interface operating system and graphical user interface operating system.

Command or Character based User Interface (CUI)

CUI is a traditional user interface. It provides the interactive terminal where user can enter the command to interpret. It is the only one common place where the program and the user communicate with each other.

Graphical User Interface (GUI)

With advancement of technology, computer system has become quicker and cheaper. Operating environment has also changed. This lead the development of graphical user interface where users can interact with the computer using picture and graphs, rather than character and commands. It displays the icon, buttons, dialog box etc. Popular GUI based operating system is Microsoft Windows.

Functions of OS

• It manages the job waiting to be processed. It recognizes the jobs, identifies their priorities to process.
• It manages the storage and retrieval of data.
• It is used for the virtual memory management. With this software it is possible to increase the capacity of main memory without actually increasing its size but using secondary memory as primary memory.
• It manages the input and output operation of computer.
• Its job is to secure data inside the memory of computer. It protects hardware and software from improper use. Some large operating system provides password also for the purpose of security.
• It communicates with all the hardware and software components of computers.
• It helps to interpret the command given by the user to computer system.

Virtual memory

Virtual memory is a feature of an operating system (OS) that allows a computer to compensate for shortages of physical memory by temporarily transferring pages of data from random access memory (RAM) to disk storage.

Virtual memory combines computer's RAM with temporary space on the hard disk. When RAM runs low, virtual memory moves data from RAM to a space called a paging file. Moving data to and from the paging file frees up RAM so computer can complete its work.

To facilitate copying virtual memory into real memory, the operating system divides virtual memory into pages, each of which contains a fixed number of addresses. Each page is stored on a disk until it is needed. When the page is needed, the operating system copies it from disk to main memory, translating the virtual addresses into real addresses.