Computer 10

Networking and Telecommunication, Internet and Its Services, Computer Security, Computer Virus, Multimedia and Its Application, Cyber Law and Computer Ethics, Number System, Database Management System (MS Access), Modular Programming, Sequential File Handling, C Programming Basics

Telecommunication and Networking

1.a. Communication : The process of exchanging views, ideas or information between two or more persons or device is called communication. Example . Telephone, newspaper, email etc.

b. Data communication: Exchanging data in form of text, sound, graphics, video etc between two or more devices in different places is called data communication. Eg. Telephone, email, chat, etc.

c. Telecommunication: Exchanging information and data inform of text, sound, video etc. between two or more devices in a significant distance is known as telecommunication.
d. Components of telecommunication

i. Sender: a person/device which sends the data to the receiver. Sender is the source of information.

ii. Receiver: a person/device who/ which receives information and data from sender.

iii. Data : It is the matter of information which is sent by the sender to the receiver. Data may be text, sound, video, graphics etc.

iv. Medium : It is the path or channel through which data transmit from sender to receiver. They are wired and wireless.

v. Protocol : It the set of rule which governs the data communication over the network devices.
e. Modes of communication:

There are three modes of data communication. They are :

i. Simplex mode : It the one way communication mode where data flow only in a direction. Eg, Newspaper, TV, Radio.

ii. Duplex mode: It is two way communication mode where data flow in both directions. It is further divided into two categories;

*Half duplex mode: Two way communication alternatively where data flow form sender to receiver first, then receiver to sender later. Eg. Email, walky- talky etc.

*Full duplex mode : Two way communication simultaneously( side by side at the same time) where data flow in both direction at the same time. Eg. Telephone, chat etc.

2.a Computer network : Computer network is defined as a physical and logical interconnection of two or more computers and devices with the help of cable or wireless media for sharing hardware ,software and information.

i. Advantages:

* Hardware resources can be shared

* Software and application can be shared

* It reduces the cost of computer installation by sharing resources.

* Fast and easy communication
ii. Disadvantages :

· Difficult to maintain data security.

· Hackers may enter into the system easily and cause loss of data.

· It is expensive to maintain and to keep system upto date.
b. Network Terminology :

i. Server : It is the powerful and main computer in network which provides services to the clients by sharing resources. It controls and manages overall network nodes. There are five types of server ;they are

* file server

* print server

* database server

* application server

* message server

ii. Client /workstation/node : Computers and devices attached to the network is called nodes. They request for data and services to the server to be accessed. Client or workstation are only computers attached under server.

ii. NIC (Network Interface card/Ethernet card ): It is an electronic board/card which is installed to all the network computers for data communication. It provides dedicated fulltime connection via cable or wireless

media among all the network computers. It is an intelligent device which acts as bridge and amplifies the signals during transmissions over network devices.

iv. NOS ( Network Operating System ) : It is the collection of powerful programs that manages and control over network system and resources. It is installed in server computer. Eg. Window 2000, windows NT, Window ME, Windows ‘7 , windows ‘8, Window Vista, LINUX, UNIX, Novell Netware etc.

v. Protocol : A set of rules and procedures which governs the data transmissions over network devices. Protocol makes logical connections among all the components and control traffic and data collision. Few examples of protocols are :

TCP/IP, FTP, SMTP, POP, NETBIOS, NETBIUE, TOKEN RING, EATHENET , ARP, VOIP, APPLE TALK,PPP

vi. Media connecter: It is a device which acts as an interface between NIC and network cables. Different connectors are used for different types of cables. They are

ST/ SC --- Fiber optic cable

RJ- 45--- Twisted pair cable( STP and UTP)

BNC/T connector --- Coaxial cable

vii. Bandwidth : It refers to the data handling capacity of transmission ( communication media). It measures the amount of data transmission per second over a communication channel. bps ( Bits per second is a unit of bandwidth measured in digital device, where as cycle per second( Hz) is unit of bandwidth in analog device.
3.a Communication media / Channel

Definition : It is defined as a path or channel through which data or signal flow in electromagnetic form from one device to another or in a specific direction.

There are two types of communication channels viz;

i. Wired( Bounded) transmission media

ii. Wireless( Unbounded )transmission media

i. Wired / Guided transmission media: The path or channel where data or signal flow through physical cable connection from one device to another in a specific directions. The types of wired media are as follows

a. Twisted pair cable : It the combination of two insulated copper wires twisted together in pair to form a cable for transmission. It is further divided into two types :

* UTP ( Unshielded Twisted Pair): It is the combination of two unshielded wires twisted around each other to carry the signal through cable. It is very common, popular and less expensive. It has maximum transmission rate ie, 1 Gbps. It is commonly used in Star topology and is available in 7 categories ( Cat 1 to cat 7).

*STP( Shielded Twisted pair) : It consist of two twisted pair copper cables are separately wrapped in a metal sheath to provide better noise protection from external disturbance. It is expensive and difficult to install. It covers maximum 90 mt.

b. Co-axial cable : It is made up of copper wire in center and surrounded with insulator. The center wire carries the data signal. It provides better noise rejection. It is used in bus topology as well as TV signals. Its maximum speed is 10 Mbps.

c. Fiber optic cable: It is the collection of thin transparent fiber glass in a bundle ( cladding) through which data travels in pulse of light. It is made up of pure silicon dioxide. It transmits the data 2 billion bps. In a half inch bundle, 50,000 thin glass fiber can be bundled together. It is used for broad band media for longer distance. It is secure because it is immune to electromagnetic interference. It is used for networking
ii. Wireless / Unguided transmission media:

The path or channel where data and signal flow without physical cable connection is called wireless communication channel. Data and signal flow in electromagnetic form through air, laser beam or vacuum. The types of wireless media are as follows:



a. Radio wave: it is a wireless transmission media through which data and signal flow in radio frequency(RF). It is used to send radio signal in far and distance by modulating radio wave into following different frequency. They are :

* FM (Frequency Modulation)

*PM ( Phase Modulation)

* AM ( Amplitude Modulation)

b. Micro wave Transmission: It is wireless transmission media where signal are sent via electromagnetic pulse between two visible tower(antenna) covering maximum 40km distance. It provides a good bandwidth and useful for MAN. Obstacle like tall building, mountain etc disturb the communication , so it is also called line of sight transmission.

c. Infrared transmission : It is a type wireless transmission media where signals are sent via pulses of infrared light. It is used for LAN.

d. Satellite transmission: It is a broad band wireless transmission media which is used to transmit radio and TV signal, internet and telephone data over longer distance. It is faster and cheaper to transmit data all over the world .Generally, it is placed 36,000 Km above the earth’s surface.
4.a Network categories ( Types of Network )

On the basis of distance and size computer network is divided into three categories . They are as follows:

i. LAN (Local Area Network): Interconnection of Network computer and devices inside a room or building via wired or wireless media is called LAN.

Features:

*It is owned by single person/organization.

* It uses cable or infrared or short radio frequency for data transmission.

* It is installed inside building or a room covering maximum5 km. distance and distance between one node to another is 1 m to 1 km..

ii. MAN( Metropolitan Area Network ): It is a network of computer that spans over a city or town in a same geographical region. It is used to link between offices in different location of the same city. Eg. Network of Himalayan bank, cellular phone etc.

Features :

· It is owned by single or multiple organization.

· It uses microwave or fiber optic cable for communication.

iii. WAN( Wide Area network): It is a network of computers that spans over a large geographical area covering different countries, cities or provenances. It covers all LAN and MAN together and make a huge network.

Features :

· It uses Public transmission media like telephone and satellite

· It is owned by multiple organization
5. a Network models ( architecture):

The design pattern of LAN networks are as follows.
i. Centralized computing network :

It is a network of computers where there is a central computer called host for data processing and storing

,and other computers connected to it called terminal. It is used by large business organization for huge data processing. It is also called host- based networks.

ii. Client server networks : The network model where there are one or more servers and others are workstation is client server network. Server shares the resources, and control the workstations. It is considered to be the best network model because it maintains data security and manages central control over all the clients. The server always must be on and it is good to connect server wit UPS for regular power supply.



iii. Peer to peer network : A group of computers that acts as both server and workstation is called peer to peer network model. All computers in networks aer equal for providing and using resources. It is useful in very small organization but it does not maintain data security. It is inexpensive network model.


6.a. Netwok Topology :

Physical arrangement of network computers and devices and cables in a LAN is called network topology. It is the arrangement pattern of LAN computers for communication. There are 3 types of topology; they are as follows:

I. Bus topology : A pattern of network where all the computers and devices are connected to a single cable ( trunk) is called bus topology. The devices are connected to both sides of a trunk via nodes. Information flow through the entire length of cable unless they are taped by any nodes. It uses Ethernet protocol. Advantages:

· Less expensive because it requires less cable

· Easy to install and add new node
Disadvantages:

*The length of the cable limit the nodes to be added.

*Traffic will be slower if more nodes are added.

*If there is wrong in cable whole system will go down.

ii. Star topology : It is a network pattern where all network computers and deices are arranged in star pattern connected through central device called hub.

Each node and server are connected to each other to the hub for communication. It uses Ethernet protocol.
Advantages :

· It is easy to install and reconfigure

· More nodes can be added or removed as required

· It is suitable for smaller as well as bigger size of network.
Disadvantages:

· It requires more cable and hub ,so it is expensive.

· If there is wrong in hub, whole network will go down.

iii. Ring topology : A pattern of network where all computers and devices are arranged in a circular loop connecting all the nodes via single cable. It connects all workstation and server through a short (fiber optic)cable. It is suitable smaller network. It uses token ring protocol.
Advantages:

i. It is cheaper and suitable for small organization.
Disadvantages:

i. It is difficult to reconfigure.

ii. If one system fail , whole network will come to the end.
7. Network communication device.

i. Bridge : It the the device which communicates between two or more similar network patterns and protocol. It receives and sends the data packet where the address is matched.

ii. Router : It is a network communication device which exchanges data between two or more different network shaving same protocols.

iii. Gateway: It is a device which convert and communicate the data over two or more completely dissimilar networks pattern and protocol. It is mostly used in intranet and internet.

iv. Hub : It is a device used in star topology as a central control for data communication. It connects all network components to its node . It is also called multi port repeater.

v. Repeater: It is a network component which receives the weak signal, amplify them and forward to the destination device. It makes the communication faster in longer distance.



vi. MODEM: It is a device which communicates with other computers connecting through telephone line. It receives the analog signal via telephone line and convert into digital pulse called demodulation similarly, while sending the data, it converts the digital signal into analog signals called modulation. There are two types of modem viz; internal modem and external modem .




Internet :


THE INTERNET AND ITS SERVICES



It is a system of network where millions of computers all over the world under various network type are collected via TCP/IP. It is an information highway and provides information of various types through web sites. The first internet is ARPANET developed by DOD in 1969 AD.

Intranet : It is a private global network which can be accessed by only special authorized organization and individuals. For example, milinet.
Requirements for internet connections:

i. A computer system with SVGA monitor.

ii. A modem connected to telephone line or wireless transmission device.

iii. Internet application software ie. web browser

iv. Registration to ISP
Internet services :

Internet provides the following services:

i. www:- It is a leading information exchange service of the internet. It links text, graphics, sound, video etc. files and display them via single interface using http. It helps user to interact with applications through dialog box and links. It is also known as web. It is developed by Timothy Berners-Lee.

ii. Email:- Electronic mail( e_mail) is the process of sending and receiving message from computer to computer over the internet. It can transmit message in form of text, video sound ,graphic etc for communication.

Advantages:

* It is cheaper, faster and reliable

* video, graphic and sound can be attached.

* Multiple copies of the same message can be sent to many person at ease. Disadvantages :

* Real time communication ( at the same time ) is not possible.

* Hacking and phi sing of message are possible threats which may trap and destroy our message.

Email uses two protocols viz; POP and SMTP

SMTP (Simple Mail Transfer Protocol):It governs the transmission of email message from user computer to server and, vice versa.

POP( Post Office protocol): It governs the storing of email message in mailbox ie. inbox and outbox.

iii. IRC( Internet Relay Chat) : It is the service of internet which allows user to communicate in real time using text and sound. It facilitates user to talk with one or many friends on line. It is faster and cheaper methods of communication.

iv. E-Commerce: It is the process of buying and selling products and service on line. Companies host the website which includes details about products, information, methods of transaction etc. the buyer sends the payment through credit card or visa card.

Advantages:

* Easy to expand market.

* Reduce the cost of holding stock

* Payment can be made via credit card or visa card. Disadvantages:

· Feeling of insecurity of credit card discourages the customers.

· Products can not be examined physically.



V. Telnet(Remote login) : It is a service of internet which allows user to access remote computer(host) from local computer online. For this, a user requires to supply password to login remote computer.

vi. File Transfer( FTP) : FTP is a program that facilitates user to search, locate and transfer a file or program from user computer to remote computers, and vice versa.

Uploading : The process of transferring a file from user( local) computer to server( remote) computer on line is called uploading, and the reverser processing is termed as downloading.

The popular FTP programs are CuteFTP, WS_FTP etc.

vii. Video conferencing : It is the process of transferring video/sound/image and information to and fro between different persons located in different places from computer to computer online. One can hear and see each other while communicating. It is useful for conducting meeting even members are not together. It requires headphone, web camera and speaker for communication. The popular software for video conferencing is Cu_SeeMe

viii. News group (Usenet) : This service allows group of internet users to exchange the view/ideas/information on any common topics. The topics may be any subject matter but should be common interest for all. One can post the information to the notice board using special software BBS( Bulletin Board Service). Then the message can be read by the members who belongs to the same new group.

ix. E_fax: E_fax is a program which allows user to send and receive fax message on the internet. By using fax application and modem, user can receive the message in hard copy. E-fax is run and governed by ‘faxway.com’ server.

Difference between E-fax and E_mail
E-mail E-fax

i. The message is stored n user computer. i. The received message is printed through printer

ii. It is managed by local server(ISP) or Yahoo ii. It is governed by ‘faxway.com’ server

or Hotmail or Gmail.

iii. It is cheaper. Iii. It is expensive

Terms Related to internet:

i. Web browser : It is program which enables to access internet ( locate site, download, display information on the screen.) . The act of viewing and moving documents and about different site on the net is called browsing. It helps user to navigate and surfing information on the internet. The examples of browser are : MS Internet explorer, Mozila Firefox, Gopher, Netscape Navigator etc.

ii. HTML : It is a scripting language which is used to develop web page .It uses an instruction called tag. It can access text, animation link and images to be displayed on internet page.

iii. HTTP : It is a protocol which is responsible to display hyper text from html document to internet page.

iii. Web page. It is the collection of web documents stored in web server. It includes information on various topics under hyper link.

iv. Home page : It is the first page of website which contains index and link. It is the doorway to website.

v. Web site : It is the collection of related web pages hosted by any company or organization . Each company provides an address to view information from web site.

vi. Search engine : It is the web site which helps to search web site and information on the net on the basis of keyword or keywords. It sets a link to connect to the different sites. Examples: Yahoo.com, Google.com, Lycos.com etc.

vii. URL : It is a unique address to locate the website on internet. It is written as ‘http//www.dotm.gov.np’.

viii. Domain name and domain type : (See example below:)

‘http//www.dotm.gov.np’ here , dotm is domain name

gov is a top domain level ( domain type)

np is a country level domain


Computer Virus:

Meaning : It is a computer program that replicates itself causing loss of data and program. It is developed by computer programmer using Assembly or low level language. Eg. Cbrain, Time bomb, June 12, etc.
Features:

(i) Self- replicating

(ii) Quick transmitting

(iii) Destructive
Purpose of creating Virus :

(i) To Percocet software from piracy

(ii) To delete , steal and damage data and program

(iii) To entertain user

(iv) To earn money with bad intention
Types of Computer virus :

(i) Boot sector virus: Infects boot sector of a disk.

(ii) Application infector/ File virus: The virus which infects the file having extension .com.

.exe. .drv etc is known as file virus.

(iii) Dos System infector : The virus which infects the system files of MS–DOS( IO.sys, MSDOS.sys. COMMAND. com) is known as DOS system infector.

(iv) Macro virus: Infects MS- word and Excel document template .

(v) Script virus: Infects Html and java scripting language.
Symptoms/ Indication of virus infection :

(i) Computer takes long time to boot.

(ii) Computer becomes hang and slow down, all of sudden

(iii) Size of file is changed, all of sudden.

(iv) Data and files are deleted or automatically copied.

(v) Disk drives are accessed without selection
Methods/ Modes of virus transmission/ infiltration:

(i) By using pirated software.

(ii) By using virus infected disks and games.

(iii) By down loading unknowns site and mail.
Safety from the computer virus :

(i) Do not down load or copy any program from internet, without confirmation of virus free.

(ii) Do not use virus infected disk or media without scanning.

(iii) Always use updated & latest antivirus program. ( iv) Keep back up of important data & program.

Antivirus program : A software that scans , detect and remove virus from program or computer system is known as antivirus program. The process of detecting and removing virus is called virus scanning Exampes; SCAN, CLEAN, MSAV, CPAV, AVG


Computer Security:

Meaning : Mechanism or technique applied for the protection of computer hardware and software is known as computer security. The enemies of computer are dust particle, virus, extreme temperature, faulty wiring etc.
Hard ware security :

Techniques/ mechanisms for the protection of hardware equipments of computer system is called hardware security. Some of the hardware measure are as follows:

(i) Regular maintenance : Daily cleaning of room, dust particles from computer, checking electric power and cables keep the compute system up to date.

(ii) Power protection : Computer needs 220 to 240 volt( AC) power supply for its smooth operation. So to supply the power regularly power protection devices can be used.



(a) UPS : It is an electrical device which stores the electric power in its backup battery and supplies to the computer in case of power cut off/ blackout. It is the most reliable device for continuous power supply to the computer. Therefore, it protects from loss of data due to power cut off and safeguard from short circuit. Besides UPS, volt guard, stabilizer, spike guard are also the power protection devices.

(iii) Air conditioning : Computers should be operated in a appropriate temperature. Very high temperature may expand circuit and cause slow down and hang te computer. Similarly, very low temperature may cause deposition of water particle on the circuit. Therefore, temperature between 180c to 240c shuld be maintained in a computer room. AC and Inlet/Outlet fan can be used to maintain temperature.

(iv) Dust free environment : Dust particles deposited on the circuit board, RAM , hard disk etc. may cause blockade of current and data flow or crash the hard disk. Therefore, dust free environment should be maintained inside computer room by closing windows and door , by cleaning room regularly etc.

(v) Access control : Unnecessary person should not be allowed inside a computer room. The entry and exit point can be controlled, by managing security guard, Door Lock, electronic card system etc.

(vi) Insurance policy : Incase of loss of computer property due to natural disaster, theft, robbery, malfunctioning etc, the insurance company will compensate the loss. Therefore, the organization should not suffer from economic crisis.
Software security :

Protection of program and data against virus, hacking, corruption etc. is known as software security. We can follow the following measures for software security .

a. Password: It the collection of secret code or characters which prevents unauthorized users accessing particular application or file. Password can be applied in system or in a particular file. Tips to use password.

· Use password longer than 6 characters

· Apply both alphabets and digits.

· Change the password regularly

· Do not tell or give password to others.

b. Back up : Back up is the process of storing copy of data and program in secondary storage media( floppy disk, CD, pendrive, Hard disk). In case of loss of original data and program , user can reuse/ reinstall from back up copy. In this way, backup provides security of data and program.

c. Hard lock key : It is a kind of checking point in program running time. User needs to type a password, when a software asks to type hard lock key. If it matches, the program continues, otherwise it halts. Thus, it helps to check software piracy.

d. Antivirus program( virus scanning) : Infection of computer virus cause losses of data and program . Therefore, antivirus program should be installed in a computer to detect and scan the virus. In this way it keeps the data and program safe.

e. Defragmentation: It is the process of accumulating scattered data into a particular sector of a disk, so that disk accesses faster. It increases the life of hard disk.

f. Scandisk : Process of checking condition of files and folder for bad cluster, error and lost chains from the disk. It fixes such errors and maintains the good condition of files in the disk.




Multimedia & Application:

Meaning : It is the computer technology which integrates text, sound, video, graphic and animation for information presentation.

Interactive multimedia : It is the technology where user can store, read, copy, save any subject matters according his/her wishes as needed. CD-ROM stores all multimedia technology because it can store video, sound and animation efficiently and safely. Moreover, it is portable, cheaper and reliable media.
Elements(media) of Multimedia technology :



i.Text ii. Sound iii. video iv. Animation v. Graphic
Additional hardware for Multimedia computer

Sound board/card, Speaker, microphone, CD-ROM/ DVD drive, Projector etc.
Additional Software :

i. Java programming ii. Windows media player iii. Real Judie or Shock wave iv. Active- x of open Dock v. Photoshop vi. Flash
Multimedia system VS Multimedia technology:

Multimedia system is the process of storing, digitizing, compressing, retrieving and decompressing the information with the help of a computer set, additional hardware and software. We apply this system for better presentation.

Where as, multimedia technology is the special computer technology which provides special technique to combine text, sound, video, animation and graphic for the presentation. It is stored in multimedia CD- ROM.
Application of Multimedia technology :

· Video game

· TV advertisement

· Animated Film

· Entertainment

· Virtual Reality: It is an artificial environment created with the help of computer hardware and software. It creates a real feeling to the user.

· Education sector:

-Useful for presenting lesson in the class with the help of projector so that teaching and learning will be more effective.

-Useful for self -learning technique(CAL)

-Useful for providing computer based training(CBT)
Advantages of Multimedia technology:

(i) Effective presentation of lesson in class with colourful pictures , graphic and animation.

(ii) Easy to learn with the help of sound and video

(iii) Useful in interactive web page
Disadvantages of multimedia technology

(i) Very costly for multimedia production

(ii) Requires very skilled manpower to produce

(iii) Requires very costly hardware set. (iv)Poor people can not use it due to high cost.




Cyber Law and computer ethics

Meaning of cyber law : The law which governs the internet, network, computer hardware & software as well as electronic and digital transaction is known as cyber law.
Objectives/ Purposes:

* To control and discourage the cyber crime.

* To regulate electronic and digital transactions.

International Cyber Law: In order to control computer crime and to provide security, US Govt. has passed the different laws related to IT,, which is called international cyber law. They are as follows.

(i) Fair credit Reporting Act 1970 AD

(ii) Freedom of Information Act , 1966 AD (iii)Video Privacy & Protection Act, 1974AD

(iv) Computer Matching and Privacy Protection Act, 1988

(v) Copyright Act, 1992 AD



Cyber crime : An unethical or illegal activities in computer is known as cyber crime. It includes, hacking, cracking, email_fissing, software piracy etc.

Cyber Law of Nepal ( 2061/05/ 30 BS.):

The electronic transaction and digital signature act is known as cyber law of Nepal. The act was passed in 2061/5/30 (15 Sept, 2004) and amended first time in 2061/11/28.

Purpose :

(i) To promote e_ governance.

(ii) To legalize electronic and digital transaction.
Important Provision of Cyber Law of Nepal :

(i) Punishment to hackers ( both imprisonment and fine)

(ii) Provision of providing license to IT Organization as well as customers.

(iii) Provision of legalization of electronic signature

(iv) Provision of formation of a judicial body to listen to computer related crimes.
Cyber ethics

Cyber ethic is a self guided rules / moral principles to be followed by the computer users and professionals.
Points( commandments ) of cyber ethics:

· Do not use computer to harm others

· Do not use other computer resources without permission or compensation.

· Do not use computer to steal .

· Do not snoop around others file and program.



Important Full form:




IBM = International Business Machine

ICT = Information Communication Technology DOD= Department of Defense

IEEE= Institute of Electrical and Electronic Engineer

EDP= Electronic Data Processing NIC= Network Interface Card STP = Shielded Twisted pair UTP = Unshielded Twisted Pair LAN= Local Area Network

WALN = Wireless Local Area Network MAN= Metropolitan Area Network WAN = Wide Area Network

RF = Radio Frequency

FM= Frequency Modulation PM= Phase Modulation AM= Amplitude Modulation

ADSL = Asymmetric Digital Subscriber Line

PSTN = Public Switch Telephone Network

VOIP = Voice Over Internet Protocol URL = Uniform Resource Locator FAQ= Rrequently Asked Question DNS= Domain Name System MSAV= Micro soft Anti Virus CPAV = Central Point Anti Virus NAV= Norton Anti Virus

MBR= Master Boot Record FAT = File Allocation Table

UPS= Uninterruptible Power Supply CCTV= Closed Circuit Television CVT= Constant Voltage Transformer

AC = Air conditioning / Alternate Current CD_ROM = Compact Disk Read Only Memory CD_RW= Compact Disk Re-writable

DVD= Digital Versatile Disk CRT= Cathode Ray Tube LCD = Liquid Crystal Display

LED = Light Emitting Diode





VSAT = Very Small Aperture Terminal CDMA = Code Division Multiple Access MODEM= Modulator Demodulator

ISDN = Integrated Service Digital Network TCP/IP= Transmission control Protocol/ Internet Protocol

NETBIOS= Network Basic Input Output System WAPS= Wireless Access Points

WWW= World Wide Web

HTTP = Hyper Text Transfer Protocol HTML = Hyper Text mark Up Language

ARPANet = Advance Research project Agency Network

DARPA = Defense Advance Research Project Agency

NSFNet = National Science Foundation Network Internet = Inter Network

E_mail = Electronic Mail POP = Post Office Protocol

ARP = Address Resolution protocol SMTP = Simple Mail Transfer Protocol FTP = File Transfer Protocol

Mb= Mega Byte

VDU = Visual Display Unit

SVGA = Super Video Graphic Adaptor MDA = Monochrome Display Adaptor VR = Virtual Reality

JPEG = Joint Photographic Expert Group GIF = Graphic Interchange Format

PDF = Portable Document Format IT = Information Technology

NITC = National Information technology Center NITDC = National Information Technology Dev

elopement Council

EDI = Electronic Data Interchange Bits= Binary digits

bps = bits per second BPS= Byte Per second

ASCII= American Standard Code For Information Interchange

ANSI= American National Standard Institute BCD = Binary Coded Decimal

EBCDIC= Extended Binary Coded Decimal Interchange Code

Kb= Kilo Byte




Important Words for Technical Term



Chap1:-> Computer network, data communication, bandwidth, communication channel, server, workstation( client/nodes), optical fiber, peer to peer, protocol , topology, NIC, MAN, LAN, WAN, MODEM, Hub, Repeater, Router, Bridge, Gateway



Chap2:-> Internet, Intranet, email, IRC, video conferencing, e- commerce, browser, ISP, WWW, home page, URL, Uploading, Downloading, FTP, Search engine,



Chap3;-> computer security, hardware security, software security, UPS, backup, password, scandisk, defragmentation, CCTV



Chap4:-> Virus, Antivirus, Program virus, Boot sector virus, Macro virus



Chap5:-> Multimedia, graphic, animation, speaker, microphone, VR



Chap6:-> Cyber law, cyber crime, cyber ethics, hacking, piracy, digital signature



MODULAR PROGRAMMING

Meaning : The process of developing program by dividing it into two or more manageable/functional parts ie; main module and sub module, is called modular programming.

* Main module: It the upper level part of modular programming which controls all the sub program. Mainly it is a data entry section for sub programs.

* Sub module/Procedure: It is a small program written under main module, which process the data and returns the output. There may be one or more sub modules under a main module. There are two types of sub programs viz;

i. SUB …END SUB

ii. FUNCTION…..END FUNCTION
Advantages of modular programming:

· it is easy and efficient to handle large project

· Debugging is easier.

· It reduces the task of repeated coding, since same module can be used in different places.

a. Parameter: It the list of variables or array name which are passed to the procedure formally, while declaring the function or sub procedure. It may be null.

b. Arguments : It is the list of variable, array name or constant which are actually passed to the procedures at the time of calling function. It should not be null. It is also called real or actual parameter.

c. Global variable : The variable declared outside the modules is called global variable. It can be accessed from both main module and sub module in the program. Generally, variable declared inside parameter, with Dim shared and Common shared are global variables.

d. Local variable: The variable which is restricted only inside a particular module is called local variable. By default, the entire variable is local in modular programming.

a. CALL : This statement is used to transfer the control between main module and sub procedure. Without this statement, a program does not return the output.

FUNCTION…. END FUNCTION: It is a user defined function, which accepts data, processes them and returns a value of specific type. Function… End Function marks the beginning and ending of Function procedure.

Features:

· It returns the specific type of value.

· It is recursive.

Type of function :

a) User defined function: The function defined by the user in order to return a particle type of value in the program is called user defined function. Eg. Function …End Function and Def… Fn.

b) Library function : The function which return the value and stored in Qbasic program is called library function.

Calling a Function : To execute the function by passing argument for specific data value is called invoking or calling a function. It can be called by the following ways :

· Variable method (Expression method), eg. V= sum(a,b)

· Print method( statement method) , eg: print sum(a,b)

Common Shared : This statement is used to make the variable accessible in both main module and sub module. It makes the variable global. It is declared in main module.

Syntax : CCOMMON [ SHARED] VARIABLE

Eg. Common shared n,…



Dim Shared : It makes the variable accessible by sharing it in both main module and sub module. It is also declared in main module.

Syntax: DIM SHARD VARIBLE(SIZE)as type

Eg: Dim shared P(10) as integer

Passing Arguments to procedures: When a procedures is called the calling statements pass the value to the procedure via arguments. There are two methods of passing arguments. The are;

* By value : In this method, the values passed to the procedure, does not modify its original value in calling procedure. It is done by enclosing the argument in parenthesis. Eg: Call Total( x,(y)); here ‘y’ argument is passed by value.

* By reference: In this method, the value is passed from parameters are copied to the procedure so that any changes in called procedure will affect the value in calling procedure. By default, all arguments are passed by reference in modular programming.




File Handling /Management /Organization



Meaning : File handling is the process of managing data file(s). It organizes the files by storing and retrieving data to and from the data file.

File : File is the collection of related data and information in a computer. There are two types of file.

(i) Program file : It is the collection of commands and keywords sequentially, in order to solve a particular problem. Program file is developed in programming language. It has an extension .BAS, .PRG,. CPP etc.

(ii) Data file : It the collection of data under different fields of a particular topic stored in computer It is linked with program file. There are two types of data file. They are

(a) Sequential access data file : The data file where data are organized in form of records sequentially, one after another. It access the records from top to bottom orderly unless end of file.

Advantages:

*. It is simple and natural way of managing data. Disadvantages:

*. It is very slow and very difficult to update the data

(b) Random Access data file : The data file where data are accessed randomly without any sequence of record is called random access data file. The address of each record is derived from the key field called record pointer. Advantages:

*. Direct access of record is possible, thus faster.

*. Files can be easily maintained up to date. Disadvantages:

*.There is danger of data corruption and deletion.
Modes of opening data file :

The way or purpose of the file to be opened is called file mode. Data file are opened to carry out the following activities.

*.To write /store data

*.To retrieve/read data

*.To append/add data

There are three modes of opening data file. They are

(i) Output mode : Data file is opened in this mode,in order to write or store data to the sequential data file.

(ii) Append mode : Data file is opened in this mode, to add/append data at the end of existing data file.

(iii) Input mode : Data file is opened in this mode, to read or retrieve data from sequential data file.
Keywords related to data file:



(i) OPEN: This statement is used to open the data file for reading or writing or adding data to the data file. It creates buffer to the memory for I/O operation.

Syntax: OPEN<file$> FOR MODE AS #<FILE NUM>

(ii) CLOSE : It terminates or closes all open data files and devices.

Syntax : CLOSE #<FILE NUM>,#<FILENUM>,…

(iii) WRITE # : This statement is used to write/store data to the sequential data file.

Syntax: WRITE#<FILE NUM>,data,……

(iv) PRINT #: : It is also used to write/store data to the sequential data file. Syntax: PRINT#<FILE NUM>,data,……

Difference between WRITE# and PRINT#

WRITE# writes the data by enclosing string data in quotation marks and separates each data by comma., where as PRINT# does not enclose string data in quotation marks, nor it separate each data by comma.

(v) INPUT# : It reads each data from sequential data file and store them to the corresponding variables.

Syntax: INPUT #<FILE NUM>, Variable list,…

(v) LINE INPUT# : It reads entire line/complete record ( maximum 255 characters) from data file and store them in a string variable.

Syntax: LINE INPUT #<FILE NUM>,String var.

(vi) FILES: It displays all the files of current drive. Syntax: FILES<Path$>

Eg : Files “c:\qbasic”

(vii) SHELL: It is used to go to DOS prompt temporarily..

Syntax: SHELL

(viii) KILL : It deletes the file(s) from specified drive and path. Syntax: KILL <Path$>

Eg : KILL “c:\qbasic\tt.dat”

(ix) SYSTEM: It is used to close Qbasic program.

Syntax: SYSTEM

(x) MKDIR: It is used to create sub directory in specified drive and path. Syntax: MKDIR<Path$>

Eg : MKDIR “c:\qbasic\QB”

(xi) CHDIR: It is used to change into current directory.

Syntax: CHDIR<Path$>

Eg : CHKDIR “c:\qbasic\QB”

(xii) RMDIR: It is used to remove sub directory. Syntax: RMDIR<Path$>

Eg : RMDIR “c:\qbasic\QB”

(xiii) NAME …AS : It is used to rename file. Syntax: NAME <OLD FILE> AS <NEW FILE> Eg. Name “Temp.dat” AS “book.dat”

(xiv) INPUT$() : It reads the specified number of character from each record of data file. Syntax: INPUT$ [n%, #<File Num>]

Eg. INPUT$ (4, #2)

(xv) EOF() : It is a flag which tests end of file. Syntax : EOF<File num>

Eg : EOF(2)


MS- Access[ Database]


Database Terminology :

1) Data : Data is the raw fact which may or may not give any sense. It is a set of static value which are stored in a table.

2) Information : It is the proceed data or output which is obtained after manipulating raw data.

3) Data Processing : The act of processing/ manipulating raw data in order to obtain meaningful information s called data processing. The steps of data processing are :

Data collection à Filing ---> Codingà Data EntryàData updating à Data Processing à Decodingà Report Printing

4) Database : It is an organized and systematic collection of data of a particular subject which is easily accessed , edited and managed.

Eg. Telephone directory, marks ledger, Salary sheet etc.
a) Importance / Advantages of database:

· Data can be stored in a small area

· Saves time in searching, updating and editing data in computerized data base.
5) Computerized VS Non computerized database :

Database organized in computer using electronic device and software is called computerized / electronic database. Whereas database in sheet of paper, organized manually is known as non- computerized database. Computerized data base access data conveniently, updating, editing and deletion of records will be faster, stores large number of data in a small device.

But non computerized database is very difficult to access, update and find the data. It creates problems while handling larger amount of data.

6) DBMS( Database management System):

It is the collection of software that manages manipulate, analyze data in database. It collects the data in a table, process them and provides required information.

Example : MS- Access, Dbase, Foxbase, Foxpro, Oracle, Clipper, Sybase,

Features/Functions of DBMS :

· Maintains data validity

· Controls data redundancy( duplication)

· Provides facilities for sharing of data

· Maintains standardization of data
7) Elements of data base :

(i) Field : It is the column heading of a database. It is the smallest unit of database where similar type of data are stored. It is also known as attribute. Eg, Name, Age, Address, Phone etc.

(ii) Record: A record is a collection of multiple related fields, which gives a complete information about an individual. It is a row in a database which is also known as tuple.

(iii) Cell : An intersection of row and column form a cell which contains a data.

7. MS- Access : It is a relational database management system that arranges data in tables, allows user to query data, and provides information through report. It is developed by Microsoft Corporation US, and available under MS – Office family.

Features of MS- Access :

· Relational database management system.

· It incorporates SQL and VB language.

· Query, form report are the useful objects.


8. Objects / Elements of MS- Access( DBMS):

(i) Table (ii) Form (iii) Query (iv) Report

(v) Pages (vi) Modules (vii) Macros


Meaning :


Table :



It is the primary object and basic structure of DBMS. It collects the data about the specific topics in row and columns. It is also known as relation.
a) Importance/Advantages of Table :

(i) It facilitates storing, grouping and sharing data

(ii) It is the basic structure of DBMS for storing information
b) Elements/ Parts of a table :

i) Fields, Records, primary key, cell etc. are the elements of table.

ii) Primary Key : A primary key is the field that uniquely identifies record in a table. Primary key that consists of two or more attributes( fields) is called composite primary key. The main feature of primary key filed are – it does not hold duplicate data nor it accepts blanks( null) data.

Advantage/ Importance:

· Primary key field controls data redundancy.

· It allows to create relationship between two or more tables.

· Facilitates data searching and sorting.

iii) Foreign key : It is the key fields that links a primary key fields from another table.

8) Sorting : Grouping records in ascending or descending order on the basic of one or more field(s) is known as sorting. Its advantages are ; (i) Since, it arranges the data in particular order, it helps to locate the data easily in a table. (ii) It increases the readability of data in a table.

9) Filtering : It is the process of extracting data from underlying table. It provides the data from the table, which meets the given criteria. There are three types of filtering;

i. Filter by form

ii. Filter by selection

iii. Advanced filter

10) Indexing : It is the process of organizing data such way, so that searching and retrieval of data would be faster. MS- access supports two types of indexing;

i. Unique index : Accepts no duplicate value

ii. Duplicate index: Accepts duplicate value in the fields.

Advantages: It control data redundancy. It speeds up data searching in the table.
11) Methods of creating /opening table.

There are basically three ways of creating table.

a) Design View

b) By entering data( Data sheet view)

c) Using wizard

a) Design view : Design view allows user to create table by defining field size and field properties. A design view window is split into two parts i.e. Filed grid pane and field property pane. User can easily modify the table structure in this view.

b) Datasheet view :It allows user to create table by entering data directly. Field names are defined by the user as a column heading by renaming the exiting fields. Data can be entered, edited and deleted in this view, easily.

c) Using wizard : It allows user to create table by selecting the pre- defined fields name, size and properties.


Design View VS Datasheet view

i. Fields size and properties can be defined in design view, where as they can not be defined in datasheet view.

ii. Table structure can be modified in design view but not in datasheet view.

iii. Direct data entry, editing and deleting are possible in datasheet view, where as they are not possible directly in design view.


Data Type supported by MS- Access

Data types are attribute for a field which determines what type of data the field contains. Access supports following Ten types of data.


Data Type

Description

Size

Example


1. Text

Accepts alpha numeric

characters. Default value 50

0 to 255

characters.

Name, Address


2.Memo

Alpha numeric characters with

punctuation marks. Used for long description

0 to 65,535

character

Remarks, Description, Auto biography


3. Number

Byte, Integer, Single, Double,

Long integer, decimal

1, 2,4,8,8 bytes

Population, Area, Length


4. Currency

Monetary data with currency

symbol.

8 bytes

Tax, Fee, Salary


5.Date & Time

Date and Time value. Date

range 100 to 9999 years

8 bytes

Date of Birth, Time of Arrival


6.Autonumber

Sequential or random number,

data entry not required

4 bytes

Serial number, Code number


7. Yes/No/

Boolean

Logical data type. Format:

True/False, On/Off

1 bit

Gender, cash/credit


8.OLE Object

Picture, sound, video

Upto 1 Gb

Map Of Nepal, music video


9. Hyper link

A link address

Upto 2048 chr

URl, Email address


10. Look up wizard

Data from another table/ combo box or list box

4 bytes

List of month, List of districts

The Field Properties:

The field properties area are the attribute of field which provides the control over a field. Different data types have different filed properties .They are as follows .




Field Property

Description


Size

Sets the maximum size of data accepted by the field.


Format

Displays data in different format. Text and Memo data type uses ; @,&,>,<

Date & Time uses ; General Date/time, Long date/Time, short date/Time, medium date/Time


Caption

Label or explanatory name for the field name. Maximum upto 2048 characters.


Default Value

Automatically repeats/sets the value in a particular field of each record ,while entering

data in the table. It is not applied to Auto number and OLE Object.


Validation Rule

To limit the values to be accepted by the field. Eg; not null, >100, between 1 and 100 etc.


Validation Text

Sets the message, when validation rule is violated . Eg; ‘Enter less than 100’ etc.


Required

Sets whether the value required or not. It is set to Yes, if data entry required other wise

No.


Indexed

Speeds up data searching and retrieval. It has two option.

i. No( no indexing)

ii. Yes (duplicate OK) Yes( No duplicate)


Input Mask

Pattern/ way of data to be entered and viewed .





Rules for naming Field:

*. A field name can be upto 64 characters.

*. It can contains letters, numbers, spaces and other symbols except perid(.), exclamation(!), acent grave(~), and brackets ([]).

FORM

Form is a database object that can be used to enter, edit, or display data from a table or a query. It provides the interface between MS Access and user because it displays the records on the screen. There are two types of from; i. Main form ii. Sub form



Methods of creating form :

i) Design view

ii) Auto Form

iii) Form wizard

Layout of Form :

i) Data sheet

ii) Tabular

iii) Columnar

iv) Justified

Control of Form:

Tab, Radio Button, Check box, List box, Combo box, Option group, command button etc.


QUERY

It is an object of MS Access which is used to view, change and analyze the data in different ways from table or query. It asks a questions about the data stored in the tables and returns the results. It uses criteria to analyze and extract the require information.

Types of Query:

1. Select Query : It retrieves the data from one or more tables or queries and displays information bys using given criteria.

2. Action query : The query which directly changes or moves one or more records in one operation . It deletes, update and group the records.

a) Update query: It makes global changes to a group of records in one or more tables.

b) Delete query: It deletes one or more records from one or more tables.

c) Append query : It adds a group of records from one or more tables to the existing table at the end of record. d) Make table query : It creates a new table from all or part of the data in one or more tables for a backup copy of a table.

Besides above, Cross tab query, SQL query and Parameter query are also the different types of query.



Criteria : Criteria are the expression that defines on e or more condition in order to obtain specific set of records or data from query or filter. Eg. Like , Not like, Between , <>100 etc.

Operators : Operators are the sing or symbol or words that are used to compare and calculate the data in query. Access supports the following type of operators.

i. Arithmetic operator : +, -, *, /, \. MOD

ii. Comparison Operator: =, >, <. >=. <= , Like, Not Like, In, Between

iii. Relational operator: AND, OR, NOT


REPORT

It is a database object which provides the information in printed form. It groups and presents the formatted information from underlying table, query and SQL statement.

Methods of creating Report :

iv) Design view

v) Auto Report

vi) report wizard

Layout( Print view) of Report :

i. Tabular

ii. Columnar

iii. Justified



Different parts of Report :

i. Report Header : It contains the title of report.

ii. Page Header : Information contains at the first of each page

iii. Detail: Display detail information from selected fields.

iv. Page Footer : Information contains at the last of each page

iv. Report footer: It contains the information at the end of report.


Page Orientation of Report :



· Portrait : Vertical Orientation of page

· Landscape : Horizontal orientation of page.