I won't type any long details. As the title suggests, this article is about some concepts of Information Technology.
Hope this helps & please comment if you have any queries.
Abbreviations
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o STD – Standard Trunk Dialing
o ISD – International Subscriber Dialing
o SMS – Short Message Service
o MMS – Media Message Service
o PABX – Private Automatic Branch eXchange
o CDMA – Code Division Multiple Access
o GSM – Global System for Mobile communication
o ENIAC –Electronic Numerical Integrator and Calculator (1946, First Electronic Computer)
o EDVAC – Electronic Discrete Variable Automatic Computer
o CPU – Central Processing Unit
o ALU – Arithmetic and Logical Unit
o RAM – Random Access Memory
o ROM – Read Only Memory
o CLI – Command Line Interpreter
o GUI – Graphical User Interface
o BIOS – Basic Input Output System
o IBM – International Business Machines
o DTP – Desk Top Publishing
o LINUX – Linus Uniplexed Information Computing System (Graphic User Interface)
o UNIX –Uniplexed Information Computing System (Character User Interface)
o DOS – Disk Operating System
o WINDOWS – window for computer
o FAX- Facsimile Machine
o MICR – Magnetic Ink Character Recognition
o OCR – Optical Character Recognition
o OMR – Optical Mark Recognition
o ASCII – American Standard Code
o BIT – Binary Digit
o MIDI – Musical Instrument Digital Interface
o MPEG – Moving Pictures Expert Group
o JPEG – Joint Photographic Expert Group
o AVI – Audio Visual Information
o PNG – Portable Network Graphics
o BASIC – Beginners All Purpose Symbolic Instruction Code
o COBOL – Common Business Oriented Language
o FORTRAN – FORmulaTRANslation
o ANSI – American National Standards Institute
o URL – Uniform Resource Locator
o ISDN – Integrated Services Digital Network
o VSAT – Very Small Aperture Terminal
o TCP/IP – Transmission Control Protocol/ Internet Protocol
Generations of Computers
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o 1st Generation Computers – Vacuum Tubes
o 2nd Generation – Transistors
o 3rd Generation – Integrated Circuits (Chips)
o 4th Generation – LSIC, VLSIC
o 5th Generation – Thinking Machines (Turing Machine)
Types of Computers (based on electric signal)
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o Analog – flight simulators
o Digital – commercial and control systems
o Hybrid – ECG machines, Modem
Types of Computers (based on Size)
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o Microcomputer – 8bit microprocessor chips, IBM PC
o Minicomputer –
o Mainframe computer – DEC, ICL, IBM 3000 series
o Super computer – CRAY YMP, PARAM, CRAY2, NEC SX-3
Other Important Points
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· Natural Languages – LISP, PROLOG
· Transistor (1959) – an electronic device which can replace several hundreds of Vacuum Tubes
· Characteristics of computer – speed, accuracy, versatility, diligence, storage capacity
· Bootstrap loader – The initial startup program which is stored in ROM and whose function is to start the operation of the computer system(booting) once the power is turned on.
· RAM is a primary memory and volatile memory which has limited storage capacity.
o Primary memory is accessible directly by the Processing Unit
· ROM – It stores some standard processing programs supplied by manufacturer to operate PC
o Storage of program and data in ROM is permanent.
o ROM can only be read by CPU but it cannot be changed.
· PROM(Programmable) – In PROM, possible to store program but can’t be altered or erase later
· EPROM(Erasable, Programmable) – Overcomes the problems of PROM and ROM
o Inf. Stored in EPROM is erased by exposing it to UV light.
· EAPROM(Electrically Alterable) – memory can be altered by using electric signals
· Cache Memory – small memory chip attached between CPU and Main memory. Accessed much faster than conventional RAM.
· Secondary Memory(Auxiliary Memory) – two types: Magnetic & optical
o Magnetic – hard disk – stack of metal disks sealed in a box(rewritable)
o Optical – CD, DVD, Pen drives, zip drives
§ WORM – Write Once Read Many
· IN/OUT devices:
o Input – Keyboard, Mouse, Trackball, light pen, touch screen, MICR, OMR, BCR, Scanner
o Output – Monitor, Printer, Plotter, FAX(Facsimile Machine), Speakers
§ Printer types:
· Impact – Dot Matrix, Character printers
· Non Impact – InkJet, DIskJet, Laser, Thermal Printers
· Software – Set of programs (or instructions) that makes hardware perform set of tasks in particular order
o System software – MS Dos, UNIX, Linux
o Application software – software for specific application
· Translators – Compilers and Interpreters
o Compiler – special program that processes statements written in a particular programming language (source code) and converts to machine code.
§ It is a translator program which reads entire program written in high level language and converts it into machine language code
o Interpreter – Translates high level language into intermediate form which it then executes. Time consuming is program is long.
§ It is a translator which converts one statement of program into machine code, execute it and then goes on to perform the same for next statement, and continues till end of program or occurrence of an error
· Computer Security :
o Virus – Program written to interface with normal functioning of the computer
§ Boot sector virus – infects bootsector in harddisk and affects partition table
§ File viruses – attach with exe files. Commonly infects files with com or exe extensions
§ System Viruses – Infects specific system files such as command.com
o Viruses can be grouped as:
§ Time bomb – It will start on particular date at particular time. Computer looses its ability to function properly
§ Trojan Horse – Enters computer via email or free programs that are downloaded
§ Worm – Infiltrate legitimate data processing programs and alter or destroy data
· Often use network connections to spread from one system to other
· Linked through communication lines
Digital Computer
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· CPU – also known as ‘Brain of Computer’
· Computer Functions – Receive inputs, Process information, Produce output, Store information
· Registers – Additional storage locations. Present in CU and ALU make processing efficient.
· Address – to locate characters of data or instructions computer stores them in location called address
· Legal aspects:
o Copyright – intellectual property; it encourages artists, designers, authors to create original works by rewarding them with exclusive right to a limited period to exploit the work for monetary gain
o Disclaimer – It is an acknowledgment by the author/ creator of web page that he doesn’t claim any accuracy, completeness, or usefulness of information and contents disclosed in web
o Digital Signature – It is an encryption and decryption process allowing both the positive identification of author of an electronic message and verification of integrity
Internet & Networking
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Ø Protocol – It is a set of rules that govern data communication
Ø Communication devices:
o Wire pairs – local telephone commn. Short distance digital data commn.
o Twisted pairs – copper wires twisted in pairs. Helps reduce cross talk, EMI
§ Comes in two forms – Unshielded and Shielded Twisted Pairs, UTP and STP
§ Ethernet – IEEE 802.3 – 4 pairs of Cu cables – both voice and data transmission
o Coaxial cable – cable TV, office buildings and LANs
o Optical Fibre – glass fibre wrapped in protected in protective layers
§ Carries data by means of pulses of light
Ø Communication Services:
o Baud rate – number of bits per second
o Narrow band, voice band, broadband
Ø Modem – A modem modulates outgoing digital signals from a computeror other digital device to analog signals for a conventional coppertwisted pair telephone line and demodulates the incominganalog signal and converts it to a digital signal for the digital device
Ø Properties of Networking:
o Facilitate communications
o Permit sharing of files, data, and other type of information
o Share network and computer resources
Ø Types of Network:
o LAN – supplies networking for group of computers in close proximity
§ Ethernet cables, hubs, and Network adapters
§ Ex – schools, colleges, firms etc.
o WAN – network which covers a larger geographical area
§ Uses communication circuits to connect intermediate nodes
§ Ex – Ethernet (Xerox), ARPANET (Adv. Research Projects Agency US)
o MAN – serves role to an ISP, but for corporate users with larger LANs
§ Ex – Cellular or mobile phone network
Ø Imp Terms:
o Voice messaging – similar to electronic mail which is an audio message
o Hub – Anything that comes in one port is sent out to the others
o Switch – similar to hub but pays attention to traffic that comes across it
o Router – it is as a computer can be programmed to understand, manipulate, and route the data its being asked to handle
o Network Repeater – repeater connects two segments of network cable, regenerates the signals to proper amplitudes and send them to other segments
§ Operates at physical layer of OSI
o Bridge – it reads outermost section of data on data packet, and tells where the message is going
§ It occurs at the Data link layer of OSI
o Gateway – it can translate inf b/w diff n/w data formats or network architectures
§ Operate at application layer. Can also operate at network or session layer of OSI
Ø CN and Communication:
o Analog signal – transmission pattern is in a continuous wave form
§ Measured in Volts and Frequency in Hz.
o Digital signal – it assumes a discrete set of values over a given range
§ Sequence of voltage represented in binary form
o Communication types:
§ P to P Commn – peer to peer or point to point – network where a single commn channel is not shared by all nodes
· Ex – MAN, WAN
§ Broadcasting - network has single commn channel that is shared by all the other nodes
· Ex – LAN
o Network Topology:
§ BUS - connects networking comp along a single cable or series of cables that are connected linearly
§ RING – network stations are connected along a single path whose ends are connected to form a circle
§ STAR – number of work stations are directly linked to central server
o Communication protocols:
§ Protocol – procedure of data transmission in form of software (or)
§ It is a set of rules that tells computer know how to interpret inf at that address
· Data sequencing, data routing, flow control, error control
o Data transmission Modes:
§ Simplex – communication takes place in one direction
§ Half duplex – commn channel is used in both directions but one at a time
§ Full duplex – commn channel used in both directions at the same time
Ø Internet (network of networks):
o Internet is not a government body. Entire authority lies with Internet Society.
o E-mail (electronic mail) – paperless method of sending messages, notes, or letters from one person to other
§ Offline editing/composing/reading can be done.
o Intranet – it is the use of internet technology for communication within the firm and those organizations and individuals with whom the firm does business
o abcdef@gmail.com
§ abcdef – local part, name of the mailbox or the destination computer
§ gmail – mail server
§ .com – type of organization on net, which is hosting the mailbox
· Com – commercial institutions or organization
· Edu – educational institutions
· Org – private organizations
· Gov – government site
· Mil – military site
· Net – Gateways and administrative hosts
o FTP – Internet utility s/w used to upload or download files
§ Can login to FTP site with username anonymous and email address as password
o TELNET (Remote Computing) – telecommn utility s/w, uses available telecommn facility and allows to become a user on a remote computer
o WWW (world wide web or ‘The web’) –hypertext based information retrieval tool
o Surfing – process of using browser to view inf on internet
o URL (Uniform Resource Locator) –the address on the internet
· Protocol is followed by a colon (http), FTP, NEWS( Usenet News groups protocol) , GOPHER( alternative transfer protocol), TELNET
· Server is preceded by (//Guide4Xam.blogspot.com)
· Each name of the segment is preceded by /
o Types of Internet connections:
§ Gateway access (Level one access) – Access to internet from a network, which is not on the internet.
§ Dial up connection (Level two) – provides conn to internet through a dial-up terminal conn
· Shell Connection – user gets only textual matter of webpage. Doesn’t support graphics
· TCP/IP – it can display both text and graphics
· ISDN – high speed internet through the use of digital phone lines
§ Leased Connection (Level three) – secure, dedicated and most expensive level of internet connection.
§ DSL (Digital Subscriber Line) – connects home or office through same telephone line that comes through street
§ VSAT – an earthbound station used in satellite commn of data, voice and video signals, excluding broadcast television.
o Spamming – Act of sending unsolicited emails
OOPS Concept
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o Object – object contains data and code to manipulate data
§ It can interact without knowing details of each other’s data and code
§ Objects are variables of type class
o Class – Entire set of data and code can be made a user – defined data type with the help of a class
o Data Abstraction – abstraction refers to act of representing essential features without including background details
o Encapsulation – combining both data and functions that operate on that data under a single unit
o Modularity – act of partitioning a program into individual components is called as modularity
o Inheritance – It is a capability to define a new class (derived class) in terms of an existing class (base class)
o Polymorphism – It is the concept that supports the capability of data to be processed in more than one form.
Hope this helps & please comment if you have any queries.
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