Software Definition Software is the name given to the computer programs that instruct the hardware how to work. Software are the instructions in the form of programs which control the operation of a computer, together with the associated documentation. Without software, the computer would do absolutely nothing. System Software System software is the background programs that control a computer system. Sys tem Sof tware act s as a me diator bet ween applic ati on pro grams and the computer system’s hardware, as well as between the PC and the user. Types of System Software There are two basic types of operating systems: Single program and Multitasking. A single program operating system allows only one program to run at a time. This means that if you are working in a spreadsheet and want to write a memo, you must shut down the spreadsheet application and open up a word processor. This is annoying, especially if you need to quote some data from the spreadsheet in you r memo! So new ope rat ing sys tems wer e des igned tha t allowed mul tiple programs to run at the same time. The simplest form is multi-tasking. What this really means is that the programs are taki ng tu rns wi th the processor. It al lo ws a si ng le user to ha ve th e spreadsheet and the word processor open at the same time, and even more. Now the user can see to copy data from one to the other. Much better!! The computer must decide on how many time slices each program gets. The active program gets the most. Next is programs that are doing things but which aren't the foreground program. Last is programs that are open but aren't doing anything. They need a little bit of time every now and then to see if they are supposed to do something yet.
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Software is the name given to the computer programs that instruct the hardware
how to work. Software are the instructions in the form of programs which controlthe operation of a computer, together with the associated documentation. Without
software, the computer would do absolutely nothing.
System Software
System software is the background programs that control a computer system.
System Software acts as a mediator between application programs and the
computer system’s hardware, as well as between the PC and the user.
Types of System Software
There are two basic types of operating systems:
Single program and Multitasking.
A single program operating system allows only one program to run at a time. This
means that if you are working in a spreadsheet and want to write a memo, you
must shut down the spreadsheet application and open up a word processor. Thisis annoying, especially if you need to quote some data from the spreadsheet in
your memo! So new operating systems were designed that allowed multiple
programs to run at the same time.
The simplest form is multi-tasking. What this really means is that the programs
are taking turns with the processor. It allows a single user to have the
spreadsheet and the word processor open at the same time, and even more.
Now the user can see to copy data from one to the other. Much better!!
The computer must decide on how many time slices each program gets. The
active program gets the most. Next is programs that are doing things but which
aren't the foreground program. Last is programs that are open but aren't doing
anything. They need a little bit of time every now and then to see if they are
Another disadvantage is that DOS has a character-based interface. A graphical
user interface is easier to the users than the character-based interface.
File Access Table(FAT)
DOS creates a FAT for each disk during formatting. Every sector on the disk is
represented by an entry in the FAT as part of a cluster. DOS looks for available
clusters when a file is enlarged or created. When DOS allocates files on a freshly
formatted disk, DOS uses the first cluster and sequences through a connected
series of clusters, leaving many never-used clusters at the end of FAT. When a
file is erased or shortened, DOS marks the released clusters in the FAT asavailable again. When a file is allocated more than one cluster, each cluster
points to the next cluster that contains more of the files. The pointer is the next
cluster number. The result is a chain of clusters that comprise the map of a file's
disk storage. Thus, FAT acts as a storage map and tells DOS exactly where to go
on the disk to get all parts of a file.
How Application Programs Run in DOS
When the user specifies the application software to work on, the RAM part of
memory is filled with that image of that software. For example, if the user wants to
use WordPerfect, the command is taken from the command line and the
corresponding software is loaded on to the RAM and it works like a word
processor.
Files on DOS Disks
The files on DOS disks have specific purposes. A COM file extension identifies a
command file. Command files are the names of external DOS commands. Files
with CPI extensions operate the display screen. A file with the DAT extension is a
data file. Files with BAT extension are batch files. AUTOEXEC.BAT is a special
batch file that runs automatically when a computer is started. EXE files are
executable program files. SYS files are system files. SYS files are used to add or
modify hardware support to the basic PC operation.
Users do not need to abandon DOS and Windows to try out OS/2. OS/2 provides
a dual boot feature that allows users to boot up in either DOS or OS/2. OS/2 uses
folders much like those on the Macintosh and on some UNIX GUIs.
Advantages and Disadvantages
Advantages: It is not affected by requirements of DOS and Windows that certain
device drivers live in the first 640KB of memory. Instead, OS/2 can load network
adapter drivers, multimedia interfaces, CD-ROM software or video drivers into
memory as required. While OS/2 works very nicely with the same FAT file system
used by DOS, its HPFS has a number of benefits. It is significantly faster, it allows
a long file name, and it supports disk drivers as large as 256 gigabytes.This operating system allows multitasking and dynamic data interchange. It also
provides common graphical user interface with mainframes, minicomputers, and
microcomputers by OS/2 WARP. OS/2 was developed to assist in the sharing of
data and programs among several microcomputers. OS/2 solidly supports Novell
Netware and TCP/IP. Most network interface cards are supported.
Disadvantages: OS/2 Shell or WARP is similar to Windows, but is not identical. It
may take users a while to adjust to some of the differences. The application
programs developed specifically for OS/2 are not as many as those for Windows,
although more and more application developers are going to converting and
developing programs for OS/2 thesedays.
UNIX
UNIX was originally developed in 1969 by K. Thompson, R. Canaday and D.
Ritchie for minicomputers in the Bell Laboratories in the USA owned and run by
AT& T. By the mid-1970s, UNIX had been introduced to University of California at
Berkeley by Thompson, then widespread into an academic world. Most computer
science departments of universities have been used UNIX. UNIX initially became
popular in industry because for many years AT& T licensed the system to
universities for a nominal fee. The effect of this was that UNIX was carried by
recent computer science and engineering graduates to their new places of
Disadvantages: The first disadvantage of the Macintosh platform is the
incompatibility with DOS and Windows (PC) applications. This has been made
Macintoshes less attractive to corporate users that want to have compatibility and
connectivity within company and between companies. However, software (e.g.,
Insignia's SoftWindows) are now available for the Mac to allow it to run Windows
on PowerMac although it runs slowly. This is a great utility for a Mac user who
needs to run DOS or Windows applications occasionally. Another solution for this
is the fact that networks connecting Macintoshes to PCs are available these days.
Types of Utilities
A utility program, also called a utility, is a type of system software that allows auser to perform maintenance-type tasks, usually related to managing a compter,
its devices, or its programs. Most operating systems include several built-in utility
programs. Users often buy stand-alone utilities, however, because they offer
improvements over those included with the operating system. There are few
types of utilities recently used:
Antivirus Programs
The term, computer virus, describes a potentially damaging computer program
that affects, or infects, a computer negatively by altering the way the computer
works without the user’s knowledge or permission. Once the virus is in a
computer, it can spread throughout and may damage your files and operating
system. To protect a computer from virus attacks, users should install an antiirus
program and update it frequently. An antivirus program protects a computer
against viruses by identifying and removing any computer viruses found in
memory, on storage media, or on incoming files. Most antivirus programs also
protect against worms and Trojan Horses. When you puchase a new computer, it
often includes antivirus software.
Spyware and Adware Removers
Spyware is a program placed on a computer without the user’s knowledge that
secretly collects information about the user, often related to Web browsing
habits. The spyware program communicates information it collects to some