Desktop Operating Systems

Introduction. An OS - Operating System is the first program loaded into a computer when it boots up. The operating system manages all the other programs that run on the computer. Some of these other types of programs are listed below.

productivity programs

word processors

spreadsheets

presentation graphics

network applications

e-mail

web browsers

ftp

multimedia programs

play audio

play movies

music sequencing

OS management utilities

disk management

virus protection

reference programs

dictionaries

encyclopedias

games

The OS performs services for the application programs that request the services through an API - Application Programming Interface. In a multitasking environment the OS allocates processor and memory resources. The OS acts as a liaison between applications and the hardware.

Interfaces. User interfaces can be divided into two main categories.

command line

original design

users type text at a prompt

faster than graphical

require fewer resources than graphical

examples

DOS

UNIX

Linux

all old mainframe OSs

most can now run graphical shells

X Window for UNIX

X Window for Linux

KDE for Linux

DOSSHELL for DOS

graphical

display images a well as text

most commands can be done based on icons

generally more user friendly than command line interfaces

drag and drop

examples

Mac OS

OS/2 from IBM

Windows 3.1

Windows 9x

Windows 2000

Windows XP

run much slower than command line but with improvements in memory and processing speeds this has become seldom important

Using Commands. Commands are used to tell an operating system what it should do. In a command line interface the user has to type in strings of characters. In a GUI the user usually tries to do things like click on icons to execute commands, though this is seldom enough. In either approach, the user's inputs are interpreted according to the programming language in which the operating system is written. This is then converted to the 0s and 1s of machine language.

Proper syntax is essential for correct execution of commands. The user needs to be concerned with things such as spacing, word order and punctuation. OSs such as UNIX and Linux are case sensitive. Windows has gotten so it ignores case in almost all instances, though you never seem to be able to know for sure.

Operating systems usually make use of additional arguments in commands in order to increase range of functionality. For example, the directory command in DOS has several different options that can impact how it functions. The following image was obtained after type

help dir

at the command prompt.

I'm assuming this image gives you a short course in one reason why Microsoft has moved beyond DOS and made a lot more money than a lot of their competition.

But, the ability to add on these extra arguments still has definite impact on the potential function of a command.

Commands in different languages can sometimes be quite similar. Probably to the dismay of their developers. For example, the following table gives a list of some commands in different OSs to view TCP/IP configuration information.

Operating System	Command
Windows NT/Windows 2000	ipconfig
Windows 9x	winipcfg
Linux and UNIX	ifconfig
NetWare	config