OPERATING SYSTEM | Definition of operating system| what is operating system?

 OPERATING SYSTEM

Definition

An Operating System (OS) is an organized collection of software programs that controls the overall operation of the computer system. It provides and directs the flow of data and instructions from one part of the computer to another. The operating system acts as an interface between the hardware and the user-level program and facilitates the execution of the program.

 The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as: Recognizing input from the keyboard, Sending output to the display screen, Keeping track of files and directories on the disk and Controlling peripheral devices such as disk drives and printers. For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop—it ensures that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.

 Operating System (O.S.) Objectives & Functions

• An operating system is a program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware.
• Three objectives can be observed:
• Convenience
• Efficiency
• Ability to evolve
• O.S. as a User/Computer Interface

Multi-user or Time Sharing: Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.

Single User OS: Supports only one program at a time. It is usable by a single user at a time. E.g. MS-DOS, PC-DOS.

Multiprocessing: Supports running a program on more than one CPU. A multiprocessor operating system can incorporate more than one processor dedicated to running processes. This technique of using more than one processor is often called parallel processing. E.g. MVS, UNIX.

Multitasking: Allows more than one program to run concurrently.

Networking OS: They are multi-user, time-sharing, and multiprocessing operating systems. E.g. UNIX, Novell, Windows NT, Windows 2000/2003/2005 Server, etc.

Embedded OS: Operating System that is self-contained in the device and resides in ROM.

Multithreading: Allows different parts of a single program to run concurrently.

Real-time OS: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.