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Fundamental Concept: Computer Operating System
Fundamental concept of computer operating system starts with the structure of the OS. Conceptually, an operating system can be broken down into the kernel, shell and system utilities. The kernel is the core of the operating system, and in some cases, the distinction between the kernel and the shell is clear; in others, the distinction is only conceptual. A process is a program in execution. New processes are spawned when needed and terminated to free memory and other resources. Files are a method of organizing the information on disk. Files are usually organized in an inverted tree-like structure. A system call is a program that requests something from the operating system.
The roles of an operating system vary with the hardware and user programs it was designed to work with. The earliest operating systems were designed to help applications interact with hardware. This has grown to the point that the operating system now defines the machine. The operating system provides an interface to the underlying hardware, the application programs, and the user.
The operating system manages
- Hardware
- CPU
- Memory
- Device Drivers
- I / O
- Applications
There are four basic types of operating systems:
- Real time operating system
- Single user, single task operating system
- Single user, multi task operating system
- Multi user operating system
History of Operating System
History of operating system was started with the first generation computers. They operated on a purely mechanical basis. There was no concept of an operating system. The user fed data and the program into the computer using punched cards. The programs were debugged using front panel switches and lights. The second-generation computers were batch systems where the jobs and instructions were put together so that they could be processed without interruptions. The third generation computers used the concepts of multiprogramming and time-sharing. Spooling batch systems were the first and simplest of multiprogramming systems. The major advantage was that the output from the jobs was available as soon as the job was completed. The fourth generation saw the advent of modern operating systems for PCs, workstations and servers and also includes networking and distributed operating systems.
The early operating systems were diverse, with each vendor producing their own operating systems specific to their hardware. This continued until the 1960s when IBM developed the S/360 series of machines, where all machines ran the same operating system, OS/360. CP/M (Control Program for Microcomputers) was the first generic operating system for microcomputers. Before CP/M, every brand of computer had its own unique operating system. Because of this, programs could not be shared between computers and software had to be rewritten for every type of computer. The nearest to the operating system was the "job control language" (JCL) required to submit a program for execution on the mainframe. CP/M was a complete software development environment that enabled to write software that was machine-independent, and move CP/M itself to other computers. OS/2 was the first operating system to provide intrinsic multitasking based on hardware support. It was text-mode only and allowed only one program to be on the screen at a time, even though other programs could be running in the background.
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