DISK OPERATING SYSTEM
MS-DOS (Microsoft Disk Operating System) is a single-user, single-tasking computer operating system that uses a command line interface (CLI).
It also works as an interpreter between user and computer.
The term DOS can refer to any operating system, but it is most often used as shorthand for MS-DOS (Microsoft disk operating system). Originally developed by Microsoft for IBM, MS-DOS was the standard operating system for IBM-compatible personal computers.
The initial versions of DOS were very simple and resembled another operating system called CP/M. Subsequent versions have became increasingly sophisticated as they incorporated features of minicomputer operating systems. However, DOS is still a 16-bit operating system and does not support multiple users or multitasking. For some time, it has been widely acknowledged that DOS is insufficient for modern computer applications. Microsoft Windows helped alleviate some problems, but still, it sat on top of DOS and relied on DOS for many services. Even Windows 95 sat on top of DOS. Newer operating systems, such as Windows NT and OS/2 Warp, do not rely on DOS to the same extent, although they can execute DOS-based programs. It is expected that as these operating systems gain market share, DOS will eventually disappear. In the meantime, Caldera, Inc. markets a version of DOS called DR-OpenDOS that extends MSDOS in significant ways.
Components of MS-DOS
MS-DOS consists of four essentials programs and a set of additional utilities. Four main programs are
• Boot Record
What is BOOTing ?
It is a process that starts up a computer.
It checks for proper functioning of all the peripheral devices attached with the system. It searches for the operating system and, when located, loads it into the main memory. OR
When the computer is switched on, the firmware program in Read Only Memory(ROM) also called Basic Input-Output System(BIOS) reads programs and data i.e. Operating System and loads it into memory (RAM). This process is known Bootstrapping(Booting). The OS once loaded takes control of the computer, handles user interaction and executes application programs. BOOTing Sequence
During Booting process, computer loads the operating system into its memory. DOS booting involves reading following files into memory namely IO.SYS, MSDOS.SYS, and COMMAND COM. The Basic Input/Output Program (IO.SYS): This program provides interface between the hardware devices and software of the system. It takes care of the keyboard input, character output to monitor, output to printer and time of the day. The File and Disk Manager Program (MSDOS.SYS) : It contains the file management and the disk buffering management capabilities. It keeps track of all the disk access of an application program and remains permanently in memory. The Command Processor (COMMAND.COM) : It is also called command interpreter. It is the program that displays the system prompt and handles user interface by executing the command typed in by the user using keyboard. The CONFIG.SYS file : This file contains reference to device drivers which are loaded when OS takes control of the computer. This device drivers are required for configuring operating system for running special devices.
The AUTOEXEC.BAT file : This is a special batch program that is automatically executed when the system is started. It can be used to define keys, define the path that MS-DOS uses to find files, display messages on the screen etc. It will be executed only if it exists in the root directory or the diskette from which the system is loaded. Each time the system is started, MS-DOS executes the commands stored in AUTOEXEC.BAT file. One can run it without restarting the system by typing AUTOEXEC at the command prompt.
Warm and COLD Reboot
Switching on of the computer from Power off and loading the operating system is called "Cold...
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