Реферат: DOS And Unix Essay Research Paper Compare

utility, to aid new users. For the first time, MS-DOS was sold in stores to the

public (previous versions were only sold to computer vendors who delivered them

with their machines) (CIT, 1-3). The MS-DOS 6 family provided more memory

management for applications such as Microsoft Windows. In addition, newer

utilities were provided for disk-defragmentation, file compression, file backups

and anti-virus checking. Other variations of MS-DOS exist, such as PC-DOS by

IBM, DOS-V, Dr. DOS and others. There is even a FREE DOS available on the

Internet as an MS-DOS clone. Although it can still be found on many computers,

MS-DOS is technically an obsolete operating system, being replaced by Microsoft

Windows. For personal computers, MS-DOS is a single user, single tasking

operating system. Single user means only one person uses the computer at a time.

Single tasking means that it essentially runs one application program at a time,

and has no inherent support for running more than one application program

simultaneously (CIT, 2). If we want to look at the basic DOS operating system

itself, there is no need to look further than three system files, command.com,

Io.sys and (in DOS6.x and earlier) Msdos.sys. These files are crucial in DOS

versions up to 6.22. Io.sys represents the lowest level of the interface and

contains the routines necessary for interfacing the OS with the system?s BIOS.

It implements MS-DOS as seen by the hardware and has default drivers for console

display and keyboard, printer, serial communications, clock, and a boot disk

drive. Msdos.sys handles the higher-level routines such as converting commands

from applications into instructions for Io.sys. It implements MS-DOS as seen by

application programs. It supports file and record management, memory management,

character device input and output, execution of other programs, and access to a

real-time clock (CIT, 3). Both of these files are in the root directory, and

both are hidden from view by default. The idea is that you are not suppose to

see them, so that you don?t do anything destructive to them (such as deleting

them). They are also read-only so that they can?t be deleted accidentally.

Command.com is the shell program which interprets user commands, presents the