descibe operating system

OS - operating system

The operating system is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs and applications. 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.


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For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop - it makes sure 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.


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Classification of Operating systems

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

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Multiprocessing : Supports running a program on more than one CPU.

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Multitasking : Allows more than one program to run concurrently.

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

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

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Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.

Interacting With the Operating System

As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.

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2.1.4 Distinguish between logical I/O and physical I/O

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3.1.1 Identify Between Resident And Transient Routines

Memory Management Memory management is concerned with managing: The computer’s available pool of memory Allocating space to application routines and making sure that they do not interfere with each other. 3.1.1 Identify between resident and transient routines The operating system is a collection of software routines. Resident routines Transient routines Routines that directly support application programs as they run Stored on disk and read into memory only when needed Example: routine that control physical I/O Example: routine that formats disks The operating system occupies low memory beginning with address 0. Key control information comes first followed by the various resident operating system routines. The remaining memory, called the transient area, is where application programs and transient operating system routines are loaded. Resident & transient routines structure

Operating Systems Definition and the Classification of OS

OPERATING SYSTEMS ( OS ) What is an operating system? An operating system (sometimes abbreviated as "OS") is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. The other programs are called applications or application programs. The application programs make use of the operating system by making requests for services through a defined application program interface (API). In addition, users can interact directly with the operating system through a user interface such as a command language or a graphical user interface (GUI). An operating system performs these services for applications: In a multitasking operating system where multiple programs can be running at the same time, the operating system determines which applications should run in what order and how much time should be allowed for each application before giving another application a turn. It manages the sharing of

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