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|Booting and Dual Booting of Operating System|
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An operating system acts as an intermediary between the user of a computer and computer hardware. The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner.
An operating system is software that manages computer hardware. The hardware must provide appropriate mechanisms to ensure the correct operation of the computer system and to prevent user programs from interfering with the proper operation of the system.
Operating System: Definition
Functions of Operating system: Operating system performs three functions:
Major Functionalities of Operating System:
The operating system as User Interface:
Every general-purpose computer consists of the hardware, operating system, system programs, and application programs. The hardware consists of memory, CPU, ALU, and I/O devices, peripheral devices, and storage devices. System program consists of compilers, loaders, editors, OS, etc. The application program consists of business programs, database programs.
Conceptual view of a computer system
Every computer must have an operating system to run other programs. The operating system coordinates the use of the hardware among the various system programs and application programs for various users. It simply provides an environment within which other programs can do useful work.
The operating system is a set of special programs that run on a computer system that allows it to work properly. It performs basic tasks such as recognizing input from the keyboard, keeping track of files and directories on the disk, sending output to the display screen, and controlling peripheral devices.
OS is designed to serve two basic purposes:
The Operating system must support the following tasks. The task are:
I/O System Management
The module that keeps track of the status of devices is called the I/O traffic controller.
Each I/O device has a device handler that resides in a separate process associated with that device.
The I/O subsystem consists of
Drivers for specific hardware devices.
The input to an assembler is an assembly language program. The output is an object program plus information that enables the loader to prepare the object program for execution. At one time, the computer programmer had at his disposal a basic machine that interpreted, through hardware, certain fundamental instructions. He would program this computer by writing a series of ones and Zeros (Machine language), place them into the memory of the machine.
The High-level languages- examples are FORTRAN, COBOL, ALGOL, and PL/I are processed by compilers and interpreters. A compiler is a program that accepts a source program in a “high-level language “and produces a corresponding object program. An interpreter is a program that appears to execute a source program as if it was machine language. The same name (FORTRAN, COBOL, etc.) is often used to designate both a compiler and its associated language.
A Loader is a routine that loads an object program and prepares it for execution. There are various loading schemes: absolute, relocating, and direct-linking. In general, the loader must load, relocate and link the object program. The loader is a program that places programs into memory and prepares them for execution. In a simple loading scheme, the assembler outputs the machine language translation of a program on a secondary device and a loader places it in the core. The loader places into memory the machine language version of the user’s program and transfers control to it. Since the loader program is much smaller than the assembler, those make more core available to the user’s program.
History of Operating system
The operating system has been evolving through the years. The following table shows the history of OS.
Examples of Operating System are
After an operating system is generated, it must be available for the use by the hardware. But how the hardware know where the kernel is, or how to load that kernel? The procedure of starting a computer by loading the kernel is known as Booting the system. Hence it needs a special program, stored in ROM to do this job known as the Bootstrap loader. Example: BIOS (boot input output system). A modern PC BIOS (Basic Input/Output System) supports booting from various devices.Typically, the BIOS will allow the user to configure a boot order. If the boot order is set to:
Then the BIOS will try to boot from the CD drive first, and if that fails then it will try to boot from the hard disk drive, and if that fails then it will try to boot from the network, and if that fails then it won’t boot at all.
Booting is a startup sequence that starts the operating system of a computer when it is turned on. A boot sequence is the initial set of operations that the computer performs when it is switched on. Every computer has a boot sequence. Bootstrap loader locates the kernel, loads it into main memory and starts its execution.In some systems, a simple bootstrap loader fetches a more complex boot program from disk, which in turn loads the kernel.
When two operating system are installed on the computer system then it is called dual booting. In fact multiple operating systems can be installed on such a system. But how system knows which operating system is to boot? A boot loader that understand multiple file systems and multiple operating system can occupy the boot space. Once loaded, it can boot one of the operating systems available on the disk. The disk can have multiple partitions, each containing a different type of operating system. When a computer system turn on, a boot manager program displays a menu, allowing user to choose the operating system to use.