Реферат: DOS And Unix Essay Research Paper Compare

software companies are derived from one of the two groupings and, recent

versions of UNIX actually incorporate features from both of them. However, UNIX

has had an unregulated history with over 200 versions (Berson, 16) existing

today. The UNIX system is made up of three primary components, the kernel, the

shell, and the utilities (which includes the file system). The central part of

the OS, the kernel is the first program to start when the system is turned on

and the last program to do anything when the system is halted. In addition to

scheduling tasks, it manages data/file access and storage, enforces security

mechanisms and performs all hardware access. The name ?KERNEL? represents

the fact that it is a program designed as a central nucleus, around which other

functions of the system were added. The heart of the operating system, it not

only interacts directly with the system?s hardware, but presents each user

with a prompt, interprets commands typed by a user, executes user commands and

supports a custom environment for each user. The two most common shells are the

Bourne shell, default for the System V, and the C-shell used mainly with the BSD

version (Osiris, 1). The utilities consist of file management (rm, cat, ls,

rmdir, mkdir), user management (passwd, chmod, chgrp), process management (kill,

ps) and printing (lp, troff, pr). In order to obtain a basic understanding of

the UNIX operating system, it is necessary to touch upon several of the

principal characteristics that have permitted it to remain competitive through

the years. 1. Advanced Administration of Processes UNIX has a process manager

known as Process Scheduler, which handles the allotment of time to each of the

processes according to the priority it was assigned. 2. Multiprocessing Many

UNIX variants allow the use of various processors to execute user tasks. This

means that UNIX has support for symmetric processing, with which it can take

advantage of the fact that there are two or more CPUs in the machine. 3. File

Management The hierarchical files system that UNIX runs, as well as file access

control and directory control have served as models for the majority of modern

operating systems such as MS-DOS, OS/2 and even Windows NT. 4. Utilities Access