Fundamentals of computer part - 2

Fundamentals of computer part - 2

System Software & Application Software

System Software: -
A computer is merely a machine that knows nothing to itself. Rather it requires instruction for each and everything it performs. These instructions are provided to it through software. The software that controls internal computer operations is known as system software.

The system software can further be classified in to following categories:

 Operating System
 Language Processor
 Device Driver
 Utility Software

Application Software: -
Application Software is a set of programs necessary to carry out operation for a specified application. Application software is basically of two types
 Packages (Readymade Software) General utilities software, mostly software suites

 Customized Software (Tailor made Software) according to a user’s need.

Operating System:
Operating system is a big collection of many system software and application
software in the form of consolidated bundle. When the operating system is loaded on computer, the computer became alive, so we can say that an operating
system is the soul of computer.

Operating System (OS), in computer science, is the basic software that controls a
computer. The operating system has three major functions:

1. It provides a platform to run any external application software on computer.
2. It acts as a bridge between user and computer.
3. It coordinates and manipulates computer hardware.
Operating systems control different computer processes, such as running a
spreadsheet program or accessing information from the computer's memory. One important process is interpreting commands, enabling the user to communicate with the computer. Some command interpreters are text oriented, requiring commands to be typed in or to be selected via function keys on a keyboard.
Other command interpreters use graphics and let the user communicate by
pointing and clicking on an icon, an on-screen picture that represents a specific
command. Beginners generally find graphically oriented interpreters easier to
use, but many experienced computer users prefer text-oriented command
interpreters.

Operating systems are either single-tasking or multitasking. The more primitive
single-tasking operating systems can run only one process at a time. For instance, when the computer is printing a document, it cannot start another process or respond to new commands until the printing is completed.
All modern operating systems are multitasking and can run several processes
simultaneously. In most computers, however, there is only one central processing unit (CPU; the computational and control unit of the computer), so a multitasking OS creates the illusion of several processes running simultaneously on the CPU.
Operating systems can use a technique known as virtual memory to run
processes that require more main memory than is actually available. To
implement this technique, space on the hard drive is used to mimic the extra
memory needed. Accessing the hard drive is more time-consuming than
accessing main memory, however, so performance of the computer slows.
Time sharing and Multi User operating system refers to those operating systems
which execute programs of several users in queue. When the processor executes
a program of a user it takes up the program of other user in the time gap while
executing the earlier program.

Types of Operating System:
C.U.I:- (Character User Interface) This is a type of operating system where only
character are used in display. It’s a very oldest type of operating system. DOS is
an example of CUI type of operating system.

G.U.I:- (Graphical User Interface) It is a modern type of operating system.
This type of operating system uses graphics and character both. GUI Operating
systems are easy to learn and work upon, at the same time interesting too.

Some G.U.I. types of Operating systems:
 MS WINDOWS
 LINUX
 MACANTOSH
 APPLE MAC
 SOLARYS

Introduction:
DOS (Disk Operating System) is an oldest type of Operating System. Disk Operating
System is abbreviated as DOS. DOS is a CUI type of Operating System. In computer
science, a generic term describing any operating system is system software which is loaded from disk devices when the system is started or rebooted. DOS is a single-tasking, single-user operating system with a command-line interface.
DOS acts on commands. Because DOS is ready to perform when given proper command hence, it is also known as Command Prompt. 
Commands are certain words of English language or short form of English words. The meaning of these word or short form is already known to DOS. Since, DOS recognized these words and hence acts accordingly. These words and short forms of the English words are better known as commands.

Internal Command:-Those commands which are already stored in the “Command.Com” file of DOS are known as internal commands. For example, CLS, VOL, TIME, DATE, COPY etc

External Command:-Those commands which are not included in the command.com file of DOS rather included in other files of DOS are known as external commands. It is formatted according to programme. For example, TREE, FORMAT, MODE etc

Introduction:
Windows is an operating system launched by Microsoft Corporation. It is totally graphical
based operating system. It also gives a platform to the application software to run on itself. In this environment user can communicate with the help of icons.

Characteristic of Windows:
1. GUI (Graphical User Interface)
2. Clip Board Memory (Cut & Paste)
3. Multitasking
4. OLE (Object Linking & Embedding)
5. What you see is what you get.
6. Plug & Play Utility
GUI stands for Graphical User Interface: This is the first characteristic of windows by which windows become so famous. Through this feature, a user can communicate with the help of Icons. (The graphical representation of any program or file is called as Icon).

Clip Board (Cut & Paste): Clip board is a memory where data is stored after using cut or copy action. This is a volatile memory because when we shutdown our computer this data will be lost. The capacity of clip board memory is 24 clips.

Multitasking: To run more than one program at a time is called as Multitasking. Since Windows allows multitasking so we can say, Windows gives a facility to the user to run more that one program at a time.

OLE (Object Linking & Embedding): Through this feature user can link their file to any another file. The facility to link any file to other file is called as linking & changing in the object or modify the file is called as embedding.

What you see is what you get: Through this facility we can print our file actually as it is
shown in the document.

Plug & Play Utility: Through this feature the computer detects any hardware port when
it is plugged into the computer system. The hardware is detected automatically and
Windows gives the facility to the user to use this device.

Different version of Windows:
Win – 3.0 , 3.1, 95, 98, 98 SE, ME, Win NT, 2000, 2000 Server, 2000 Professional, Win
XP, Win XP Home Edition, Win Server 2003, XP Professional, Win XP SP1, Win XP SP2, Win
XP SP3, Win Vista, Win Server 2008

Booting Computer in Windows mode:

When we switch on the computer, first of all it loads operating system (all necessary files of Windows to startup) in the working memory (RAM) and checks all hardware parts of computer. This process is known as booting. After booting we get a screen which is known as desktop.

Internet and Computer Notes All About Internet
1. All About Internet

Internet is a global network of computers connected by network cables or through satellite links.
It is also called the network of networks and the Super Network.

When two computers are connected over the Internet, they can send and receive all kinds of information such as text, graphics, voice, video, and computer programs.

No one owns the Internet, and no single person or organization controls the Internet in its entirety.But several organizations collaborate in its functioning and development.

Internet and Computer Notes A Timeline of the Internet

2. A Timeline of the Internet
1965: Two computers at MIT Lincoln Lab communicate with one another using packet-switching technology.
⇓
1969: ARPANET (Advanced Research Projects Agency Network) of the
US Defense Department was created. It is considered
as the predecessor to the Internet.
⇓
1972: Ray Tomlinson introduces network email.
⇓
1973: Global networking becomes a reality as the University College of London
(England) and Royal Radar Establishment (Norway) connect
to ARPANET. The term Internet is born.
⇓
1974: The first Internet Service Provider (ISP)
is born with the introduction of a commercial
version of ARPANET, known as Telenet.
⇓
1982: Transmission Control Protocol (TCP) and Internet Protocol (IP),
as the protocol suite, commonly known as TCP/IP,
emerge as the protocol for ARPANET.

TCP/IP remains the standard protocol for the Internet.
⇓
1983: The Domain Name System (DNS) establishes the familiar .edu, .gov,
.com, .mil, .org, .net, and .int system for naming websites.
⇓
1990: Tim Berners-Lee, a scientist at CERN, the European Organization
for Nuclear research, develops HyperText Markup Language
(HTML), Uniform Resource Identifier (URI)
and Hypertext Transfer Protocol (HTTP)
⇓
1991: CERN introduces the World Wide Web –
invented by Tim Berners Lee – to the public.

Internet and Computer Notes How Does Internet Work?

3. How Does Internet Work?
• The Internet connectivity is provided by Internet Service Providers (ISP) like BSNL, Airtel, Reliance, Aircel Vodafone etc.
• Your computer sends digital signals to the modem (Modulator-DEModulator).
• The modem converts the digital data into analog signals and sends it to the ISP’s local center over the telephone line.
• From there it travels through various routers and lines to reach its destination – a website server like the one of Facebook or another computer.
3.1 - IP Address
The Internet Protocol (IP) address is the "roll number" of a computer connected to the Internet.
• If you connect to the Internet through an Internet Service Provider (ISP), you are usually assigned a temporary IP address for the duration of your dial-in session.
• If you connect to the Internet from a Local Area Network (LAN) your computer might have a permanent IP address or it might obtain a temporary one from a DHCP (Dynamic Host Configuration Protocol) server.

• In any case, if you are connected to the Internet, your computer has a unique IP address.

3.2 - TCP/IP
• This is the standard protocol of the Internet.
• When information is sent over the Internet, it is generally broken up into smaller pieces or "packets".
• The use of packets facilitates speedy transmission.
• It is also a safety measure to minimize the chances of losing information in the transmission process.
• TCP is the means for creating the packets, putting them back together in the
correct order at the end, and checking to make sure that no packets got lost in
transmission.

Internet and Computer Notes World Wide Web (WWW)
4. World Wide Web (WWW)
The World Wide Web, or simply the Web, is a way of accessing information over the medium
of the Internet. It is a communications model and enables the exchange of information over the
Internet through HTTP. It was developed by Tim Berners Lee in 1990.
The Web is just one of the ways that information can be distributed over the Internet. And, we don’t use the Web to send an email, but the Internet.
Unique Resource Locator (URL):
Just like we have a postal address, resources on the Internet have unique addresses – URL.

Types of Computer Malware: Explained

Introduction

Malware stands for “Malicious Software”. It performs unwanted tasks. It may cause serious damage or invasion to our computer. Stealing data, stealing the password, infecting the computer are the examples of Malware programs. Even a pop-up advertising is a malware program.
“Ransomware” is in news these days and is malicious software that blocks access to the computer until money is paid.

Types of Malware

I. Virus (Vital information resource under seize): It is a computer program that spreads from one computer to another and it causes serious damage or harm to the computer system by deleting files, by deleting everything on the hard disk etc. The purpose of this program is to disrupt the operation of a computer system. It can even utilise an e-mail program to spread the virus to another computer.

II. Trojan Horse: It is not a virus. It is a computer program that seems to be a game but in reality, it damages the computer system once you run it. It may even erase the hard disk.

III. Worm: It is a type of software that makes use of security holes and computer network in order to replicate itself. It scans the network for machines that carry a security hole and then it copies itself there and starts replicating. Examples: Code Red, Mydoom, Brontok.

IV. Spyware: It is a malware installed on the computer systems that collects information about users without their knowledge. It can be used for other purpose of secretly monitoring users in firm, corporate. Collection of information includes visited websites, IP address, browser history etc. Examples of spyware are Click-Jacker, Key-logger.

V. Adware: The ads that automatically appear on our screen when we connect to the internet are displayed by financially supported software called Adware.

VI. Browser Hijacking Software: It is an advertising program that modifies our browser settings, displays pop-up advertisements and creates desktop shortcuts.

Some points regarding cyber crime

I. Cyberstalking: The use of internet or other electronic means to harass or stalk a group, an organisation or an individual. It is done in real time or even in offline mode.

II. Identity theft: It is an unauthorised access to someone’s identity or personal information to get financial benefits or any other benefits without the consent of that individual.

III. Phishing: It is a fraudulent practice of getting someone’s personal information such as login credentials, cards numbers etc through email.

IV. Eavesdropping: It is secretly listening or accessing someone’s phone calls, instant messages, video conference or fax transmission.

 VIRUS

When I first read about computer virus, I was surprised to know it is not ‘virus’ – but VIRUS!

VIRUS is actually an acronym for Vital Information Resource Under Siege!

Everyone says computer technology is changing every day – true – so are viruses changing and evolving every single day; thus it only makes sense we know a little about these mischief makers.

To help with the MCQs, I have italicized and bold-ended the proper terms.

Here we go:

What is a VIRUS?

It is actually a program, created by people who have knowledge to write software programs. In proper terms, it is called an ‘executable program’, with bad intentions!

Viruses are a type of malware, i.e., it is malicious software. You’ll read about it some more later…

How does it work? (Or, how does it make out lives difficult!)

A come attached with another program, and once it is in our system and we execute our program- we run the virus too!

The virus replicates itself; that is multiplies when has attached itself to a computer through an infected program.

So, suppose we download an mp3 song from some suspicious looking website, and we do not have anti-virus software on our PC, in such a case a virus may get downloaded along with the mp3.

Once, the virus is in our computer, it then starts making copies of itself on our computer. So, you can imagine, once it replicates, it must need space, thus a virus uses up the hard disk space and that makes our PC/system slow and makes it hang or crash!

What other damages does it do? (-apart from crashing our PC and frustrating us?)

Depending on what the intention of the person programming the virus was, a virus can do many different types of damages, like :

(i) modification of data (Transformers movie anyone?)
(ii) files maybe overwritten with false information
(iii) files maybe damaged, so you can not open them anymore or work on them
(iv) it may even wipe out an entire drive!
(v) it may make your system to re-boot again and again
(vi) high threat viruses which target databases of big organizations and MNCs may even leak top security information of the companies…

A Virus can be programmed to do anything, so its threat can be anything; it’s a creepy virtual world out there!

Famous Viruses?

Yep, Viruses are sometimes accorded celebrity status too!

(i) First actual virus – Creeper (1970s), detected on ARPANET.
It displayed a message on the screen, “I am the creeper, catch me if

you can!”

(ii) First actual personal computer virus – Elk Cloner (1982), it affected Apple OS

through a floppy and displayed a short poem!

(iii) First virus to hit Microsoft’s DOS – Brain (1986)

(iv) Most destructive virus – MYDoom (January 2004)

(v) Most widespread and fast spreading virus – ILOVEYOU, also known as the love letter! (2000)

Categories of Viruses?

Yes, Viruses are categorized based on what/where/how they affect.

(i)File Virus/Parasitic Virus: most of the viruses fall in this category. In this type the viruses come attached to a file, usually a file which is executable, i.e., it can be run.

(ii) Boot sector Virus: these viruses, as the name suggest, affect the boot sector. Which means it will load before the operating system. It infects through floppy disks/ hard disks drives.

Imagine, a virus loading before the operating system does! This can only mean trouble!

(iii) Macro Viruses: Macro programs consist of a set of commands which executes itself every time it is run. So, this type of virus affects a program/application/software’s macros programming feature, to infect documents.

(iv) Multipartite Viruses: spread and infect in multiple ways, they can effect the boot sector as well as infect documents/files. They can have multiple means of transmission and of infection.

6. What are worms, malware etc.?(i)Malware– is the short for malicious software, as the standard definition goes – is any software which can disrupt normal computer operation, gather sensitive information or gain access to private system.It is also sometimes referred to as badware. Malwares are essentially of two types: (1) Viruses and (2) Worms.(ii) Worms: worms are like viruses in the sense that they do the same damages that viruses do, they also replicate themselves.However the main difference being, it is a standalone malware – i.e., it does not need to attach itself to any host/executable file. It on its own actively transmits itself through a network and infects computers.In other words for virus infection to happen, a user has to actually run the virus infected program, only then will the virus program run too. But worms spread by themselves!(iii) Trojan horse: This is my favorite malware as it is named on a very interesting piece of history which involves Achilles and his heel!
   Also known as the Trojan, it is a malicious software which run without the knowledge of the user, to gather sensitive information.
   Its specialty is it can run undetected, or when the system is shut down. It can encrypt/decrypt files and documents and transmit them to those who want it.
   Trojan are disguised in the form of a legitimate and desirable program, that any user would without suspicion run. User thinks that the program it is running has nothing wrong with it, whereas the Trojan is secretly doing its work!
   Trojan can also be called a ‘Spyware’; but it is NOT a virus. Why? Simply because Trojans do not replicate like viruses do!
   (iv) Rootkits: are programs that modify setting in the operating system to keep the malwares hidden from detection.

How can we keep viruses away?

By installing anti-virus softwares!

This is probably something every one you must have heard or seen or installed one yourself!

Anti-virus software protects your system by periodically scanning its files/documents/programs to check for hidden executable programs.

It works by searching for those which are a match to any pre-defined virus already stored in its virus definition file. When there is a match, the anti-virus tells you that your PC has been infected by ‘so-and-so’ virus, and will proceed to remove it.

If it finds that there exists a program which is suspicious, but the anti-virus does not know its name, then it’ll ask you to take appropriate action.

Every other day new viruses are programmed and unleashed, and every other day thousands of e-mails are opened, movies/songs/files/softwares etc. are downloaded and these viruses find their way into out PCs.

That is why it is very essential for any PC to have an updated anti-virus all the time!

I hope this topic was informative and enjoyable!

Next time you run a virus scan on your PC, take some time and read the descriptions written alongside the viruses detected; some will be malwares, some worms and some Trojans!

Networks 

1. Local Area Network – A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. It allow
members of an organization to share databases, applications, files, messages and resources such as printers and Internet connections.

2. Wide Area Network – Wide Area Networks (WANs) connect networks in larger geographic areas like a state, a country or the world.

Wireless Local Area Network – A LAN based on Wi-Fi wireless network technology

3. Metropolitan Area Network – A network spanning a physical area larger than a LAN but smaller than a WAN, such as a city.
Eg:- A single entity such as a government body or large corporation

4. Campus Area Network – A network spanning multiple LANs but smaller than a MAN, such as on an university or local business campus.

TOPOLOGY

Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection

1. Bus topology
2. Star Topology
3. Ring topology
4. Mesh Topology
5. Hybrid Topology
6. Tree Topology

1. Bus Topology

In this topology, all yhe computers are connected to single cable.

Advantages:
1. It is easy to add or remove computers from this topology.
2. If one link fails in the network, the other workstations are not affected.
3. It is more reliable.
4. In this topology, very high transmission rates are possible.
Disadvantages:
1. It the central switch/hub fails, the whole network goes down.
2. Long cable length is required since each device is directly connected to the hub/switch.

3. It may be costly to install since long length cable is required.


2. Star Topology

In this topology, all computers are connected to switch hub.

Advantages:
1. Each computer does not have to depend on the central device as each computer controls transmission to and from itself.
2. It has short cable connection which increases network reliability.
3. It supports very high data transmission rate.

Disadvantages:
1. It is difficult to change network structure.

2. If a single computer fails, at least a portion of the network won't work.


3. Ring topology

In this topology, all the computers or devices are connected to each other in a closed loop by single communication cable. Data transfer takes place in one direction from one node to another around the ring.
It is also called loop network.

4. Mesh Topology

It is a point to point connection between every device in the network.


Advantages :
1. Failure of a device does not affect the data transmission to the destination device.
2. Easy to troubleshoot
Disadvantages:
1. It is difficult to set up.

2. It is more expensive than other topology.

5. Hybrid Topology :

A hybrid topology is a type of network topology that uses two or more differing network topologies. These topologies can include a mix of bus topology, mesh topology, ring topology, star topology, and tree topology.



6. Tree Topology

A tree topology is a special type of structure in which many connected elements are arranged like the branches of a tree. For example, tree topologies are frequently used to organize the computers in a corporate network, or the information in a database

Important Abbreviations

A

• Al – Artificial intelligence
• ALGOL – Algorithmic Language
• ARP – Address resolution Protocol
• ASCII – American Standard Code for Information Interchange

B

• BINAC  – Binary Automatic Computer
• BCC – Blind Carbon Copy
• Bin – Binary
• BASIC – Beginner’s All-purpose Symbolic Instruction Code
• BIOS – Basic Input Output System
• Bit – Binary Digit
• BSNL – Bharat Sanchar Nigam Limited

C

• CC – Carbon Copy
• CAD – Computer Aided Design
• COBOL – Common Business Oriented Language
• CD – Compact Disc
• CRT – Cathode Ray Tube
• CDR – Compact Disc Recordable
• CDROM – Compact Disc Read Only Memory
• CDRW – Compact Disc Rewritable
• CDR/W – Compact Disk Read/Write

D

• DBA – Data Base Administrator
• DBMS – Data Base Management System
• DNS – Domain Name System
• DPI – Dots Per Inch
• DRAM – Dynamic Random Access Memory
• DVD – Digital Video Disc/Digital Versatile Disc
• DVDR – DVD Recordable
• DVDROM – DVD Read Only Memory
• DVDRW – DVD Rewritable
• DVR – Digital Video Recorder
• DOS – Disk Operating System

E

• EBCDIC – Extended Binary Coded Decimal Interchange Code
• e-Commerce – Electronic Commerce
• EDP – Electronic Data Processing
• EEPROM – Electrically Erasable Programmable Read Only Memory
• ELM/e-Mail – Electronic Mail
• ENIAC – Electronic Numerical Integrator and Computer
• EOF – End Of File
• EPROM – Erasable Programmable Read Only Memory
• EXE – Executable

F

• FAX – Far Away Xerox/ facsimile
• FDC – Floppy Disk Controller
• FDD – Floppy Disk Drive
• FORTRAN – Formula Translation
• FS – File System
• FTP – File Transfer Protocol

G

• Gb – Gigabit
• GB – Gigabyte
• GIF – Graphics Interchange Format
• GSM –  Global System for Mobile Communication

H

• HDD – Hard Disk Drive
• HP – Hewlett Packard
• HTML – Hyper Text Markup Language
• HTTP – Hyper Text Transfer Protocol

I

• IBM – International Business Machine
• IM – Instant Message
• IMAP – Internet Message Access Protocol
• ISP – Internet Service Provider

J

• JPEG – Joint Photographic Experts Group

K

• Kb – Kilobit
• KB – Kilobyte
• KHz – Kilohertz
• Kbps – Kilobit Per Second

L

• LCD – Liquid Crystal Display
• LED – Light Emitting Diode
• LPI – Lines Per Inch
• LIS – Large Scale Integration

M

• Mb – Megabit
• MB – Megabyte
• MPEG – Moving Picture Experts Group
• MMS – Multimedia Message Service
• MICR – Magnetic Ink Character reader
• MIPS – Million Instructions Per Second

N

• NIC – Network Interface Card
• NOS – Network Operating System

O

• OMR – Optical Mark Reader
• OOP – Object Oriented Programming
• OSS – Open Source Software

P

• PAN – Personal Area Network
• PC – Personal Computer
• PDA – Personal Digital Assistant
• PDF – Portable Document Format
• POS – Point Of Sale
• PNG – Portable Network Graphics
• PPM – Pages Per Minute
• PPP – Point-to-Point Protocol
• PROM – Programmable Read Only Memory
• PSTN – Public Switched Telephone Network
• POST – Power On Self Test
• PING – Packet Internet Gopher

R

• RAM – Random Access Memory
• RDBMS – Relational Data Base Management System
• RIP – Routing Information Protocol
• RTF – Rich Text Format

S

• SMTP – Simple Mail Transfer Protocol
• SQL – Structured Query Language
• SRAM – Static Random Access Memory
• SNMP – Simple Network Management Protocol
• SIM – Subscriber Identification Module

T

• TCP – Transmission Control Protocol
• TB – Tera Bytes

U

• UPS – Uninterrupted Power Supply
• URI – Uniform Resource Identifier
• URL – Uniform Resource Locator
• USB –  Universal Serial Bus
• ULSI – Ultra Large Scale Integration
• UNIVAC – Universal Automatic Computer

V

• VAR – Variable
• VGA – Video Graphics Array
• VSNL – Videsh Sanchar Nigam Limited
• VDU – Visual Display Unit

W

• Wi-Fi – Wireless Fidelity
• WLAN – Wireless Local Area Network
• WPA – Wi-Fi Protected Access
• WWW – World Wide Web
• WORM – Write Once Read Many

X

• XHTML – eXtensible Hyper text Markup Language
• XML –  eXtensible Markup language

Z

• ZB – Zeta Byte

Some other Important Abbreviations – 

• OCR – Optical Character Readers
• ODBC – Open Data Base Connectivity
• OLE – Object Linking And Embedding
• OMR – Optical Mark Reader
• ONE – Open Network Architecture
• OOA – Object Orient Analysis
• OOAD – Object Oriented Analysis And Design
• OOP – Object Oriented Programming
• OOPS – Object Oriented Programming System
• OPEN GL – Open Graphics Library
• OS – Operating System
• OSI – Open System Interconnection
• PC – Personal Computer
• PCI – Peripheral Component Interconnect
• PCMCIA – Personal Computer Memory Card International Association
• PDA – Personal Digital Assistant
• PDF – Portable Document Format
• PDL – Page Description Language
• PDU – Protocol Data Unit
• PIC – Programming Interrupt Control
• PILOT – Programmed Inquiry Learning Or Teaching
• PLA – Programmable Logic Array
• PLC – Programmable Logic Controller
• PNG – Portable Network Graphics
• PNP – Plug And Play
• PPP – Peer To Peer Protocol
• PPTP – Point To Point Tunneling Protocol
• PROM – Programmable Read Only Memory
• PS – Post Script
• RADSL – Rate Adaptive Digital Subscribes Line
• RAID – Redundant Array Of Independent Disks
• RAM – Random Access Memory
• RAMDAC – Random Access Memory Digital To Analog Converter
• RAS – Remote Access Network
• RD RAM – Rambus Dynamic Random Access Memory
• RDBMS – Relational Data Base Management System
• RDO – Remote Data Objects
• RDP – Remote Desktop Protocol
• RFC – Request For Comments
• RGB – Red Green Blue
• RICS – Reduced Instruction Set Computer
• RIP – Raster Image Processor
• RISC – Reduced Instruction Set Computer
• ROM – Read Only Memory
• RPC – Remote Procedure Call
• RTC – Real Time Clock
• RTF – Rich Text Format
• RTOS – Real Time Operating System
• SACK  – Selective Acknowledgements
• SAM – Security Access Manager
• SAP – Service Access Point, Systems ApplicationsProducts
• SCMP –  Software Configuration Management Plan
• SD RAM – Synchronous Dynamic Random AccessMemory
• SDD  – Software Design Description
• SDK – Software Development Kit
• SDL – Storage Definition Language
• SDN – Integrated Service Digital Network
• SDSL – Symmetric Digital Subscribes Line
• SG RAM – Synchronous Graphics Random AccessMemory
• SGML – Standard Generalized Markup Language
• SIM – Subscriber Identification Module
• SIMD – Single Instruction Multiple Data
• SISD – Single Instruction Single Data
• SIU – Serial Interface Unit
• SMP – Symmetric MultiProcess
• SMS – Short Message Service
• SMTP – Simple Mail Transfer Protocol
• SNA – System Network Architecture
• SNAP – Sub Network Access Protoco
• lSNMP – Simple Network Management Protocol
• SNOBOL – String Oriented Symbolic Language
• SOAP – Simple Object Access Protocol
• SPX – Sequenced Packet Exchange
• SQA – Statistical Quality Assurance
• SQL – Structured Query Language
• SRAM – Static Random Access Memory
• SRS – Software Requirements Specification
• STP – Shielded Twisted Pair
• SVVP – Software Verification And Validation Plan
• SW – Software
• TAPI – Telephony Application Program Interface
• TB – Tera Bytes
• TCP – Transmission Control Protocol
• TCPIP – Transmission Control Protocol InternetProtocol
• TDI – Transport Data Interface
• TDMA – Time Division Multiple Access
• TPM – Transactions Processing Monitor
• TSR – Terminate And Stay Residents
• UDD – User Datagram Protocol
• UDP – User Datagram Protocol
• UI – User Interface
• UML – Unified Modelling Language
• UNC – Universal Naming Convention
• UNIX – Uniplexed Information And ComputerSystems
• URL – Universal Resource Locator
• USB – Universal Serial Bus
• USRT – Universal Synchronous ReceiverTransmitted
• UTP  -Unshielded Twisted Pair
• VAN – Virtual Area Network
• VAST – Very Small Aperture Terminal
• VB – Visual Basic
• VC++ – Visual C++
• VCD – Video Compact Disc
• VDL – View Definition Language
• VGA – Video Graphics Array
• VHS – Video Home System
• VLIW – Very Long Instruction Words
• VLSI – Very Large Scale Integrated Circuits
• VPN – Virtual Private Network
• VRAM – Video Random Access Memory
• VRML – Virtual Reality Modelling Language
• VS – Visual Studio
• VVR – Software Validation And Validation Report
• VXD – Virtual Device Driver
• W3C – World Wide Web Consortium
• WAIS – Wide Area Information Servers
• WAN – Wide Area Network
• WAP – Wireless Application Protocol
• WBEM – WebBase Enterprise Management
• WDM – Wave Division Multiplexing

IMPORTANT EXTENSION

The topic is File Name Extensions.

Text Files

.log: Log File

.wpd: WordPerfect Document

.odt:  OpenDocument Text Document

.pages:  Pages Document

.doc:  Microsoft Word Document

.docx:  Microsoft Word Open XML Document

.tex:  LaTeX Source Document

.wps:  Microsoft Works Word Processor Document

.msg:  Outlook Mail Message

.rtfRich:  Text Format File

.txtPlain:  Text File

Data Files

.vcf:  vCard File

.dat:  Data File

.pptx:  PowerPoint Open XML Presentation

.sdf:  Standard Data File

.tar:  Consolidated Unix File Archive

.csv:  Comma Seperated Values File

.xml:  XML File

.pps:  PowerPoint Slide Show

.ppt:  PowerPoint Presentation

Audio Files

.aif:  Audio Interchange File Format

.mpa:  MPEG-2 Audio File

.ra:  Real Audio File

.iff:  Interchange File Format

.wav:  WAVE Audio File

.wma:  Windows Media Audio File

.mp3:  MP3 Audio File

Video Files

.avi:  Audio Video Interleave File

.3gp3:  GPP Multimedia File

.flv:  Flash Video File

.mpg:  MPEG Video File

.vob:  DVD Video Object File

.mp4:  MPEG-4 Video File

.3g:  23GPP2 Multimedia File

.m4:  viTunes Video File
.wmv:  Windows Media Video File