class 10 computer

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ss 10 Notes

NETWORKANdTELE COMMUNICATION

Data communication

Data communication system is the collection of hardware, software and other devices that allows exchanging data, information and voice between two or more devices through a wire or radio waves.

Telecommunication

Telecommunication is a system if transmission of sounds, images, texts or data in the form of electronic signals.

Components of data communications

The components of data communication are as follows:

Data: This is the data that is to be communicated.

Sender: This is the device used to send data.

Medium: This is the device through which the sender makes communication to the receiver.

Receiver: This is the device which receives data sent by the sender.

Protocol: This is the set of rules that are followed nu the sender and the receiver to make communication possible.

Telecommunication

Telecommunication is a system if transmission of sounds, images, texts or data in the form of electronic signals.

Computer network

A computer network is a logical or physical interconnection between two or more computers such that they could communicate with each other.

Advantages of computer network

i. A computer networked environment allows faster, easier and reliable transfer of data files from one computer to another.

ii. A network computer allows sharing of networked connected peripherals and simultaneous access to programs and data irrespective of the physical location of the resources and the user.

iii. Computers in network can access the network connected hardware devices like printer, scanner, disk drives etc.

Three models of network

i. Client - Server Network

ii. Peer - to - Peer Network

iii. Centralized Computing Network

Client Server Network

It is a type of network in which each computer in a network is either a client or a server. It is an arrangement where some programs, files or other resources located on one computer called the server but are available to other systems on the network, called clients.

Protocols

Protocols are the sets of rules that the computer on the network must follow to communicate and to exchange the data with each other.

Names of the protocols

FTP = File Transfer Protocol

SMTP = Simple Mail Transfer Protocol

TCP/IP = Transmission Control Protocol/ Internet Protocol

ARP = Address Resolution Protocol

POP = Post Office Protocol

HTTP = Hyper Text Transfer Protocol

CDP = Cisco Discovery Protocol

Network Interface Card (NIC)

Each computer on any types of network needs a hardware component to control the flow of data. The device that performs this function is Network Interface Card (NIC), commonly called network card.

Topology

A network topology refers to the shape of the network in which all the computers are connected together.

Local Area Network (LAN)

A Local Area Network (LAN) is a network of computers that are relatively near to each other and are connected in a war that enables them to communicate by a cable and a small wireless device. A LAN consists of just two or three computers to exchange data or share resources or it can include hundreds of computers of different kinds.

Metropolitan Area Network (MAN)

Metropolitan Area Networks (MANs) are large computers networks spread over a city or neighboring cities. A MAN can have a group of many LANs. Especially, big companies, banks, offices etc. have their branches or sub offices in a city or in neighboring cities. They use MAN to connect with their branches or sub offices for communicating data and information. The communication media in MANs may be optical fiber or unbounded communication media like microwave system, infrared system, radiowave to link their branches and sub offices.

Wide Area Network (WAN)

Wide Area Network is a telecommunications network usually used for connecting computers that spans a wide geographical area. WANs can be used to connect cities, states or even computers. Typically, it will employ communication circuits such as long distance telephone wires, microwaves and satellites. WANs are often used by larger corporations or organizations to facilitate the exchange of data. The world's most popular WAN is the Internet.

[1]MODEM

MODEM stands for Modulator Demodulator. It is the device that converts digital data to analog form and vice versa. It is a device used to transfer the data of one computer to another using telephone lines.

Repeater

The signals transmitted become weak due to some problem in the transmission mediums or the distance between the two locations. A repeater is a device that amplifies the incoming signals, creates a new copy of it and transmits the signals on the network. Repeaters are required in the network where computers are a part of each other.

Hub

A hub is a hardware device that relays communication data. A hub sends data packets to all devices on a network, regardless of any MAC addresses contained in the data pocket. It is a device with multiple ports that allows network devices to be connected together. It acts as a central networking device in the star topology.

Bus Topology

A bus topology is a network topology in which nodes are connected in a daisy chain by a linear sequence of buses. It is an arrangement of computers on a local area network in which each computer is connected to a central cable through which data is channeled.

Ring Topology

Ring topology is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node - a ring. Data travel from node to node with each node along the way handling every packet

NUMBER SYSTEM

Number system

Number system is an organized and systematic way of representing numbers.

Decimal number system

The number system which is formed by 0 to 9 is called decimal number system.

Binary number system

The number system which i sformed by 0 and 1 is called binary number system.

Octal number system

The number system which is formed by eight different Digits (0-7) is known as octal number system.

Radix of a number system

The base or radix of a number system defines the range of possible values the digit may have.

Hexadecimal number system

The number and character set of hexadecimal number system are as follows:

Numbers: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Characters: A, B, C, D, E, F

CYBER LAW AND ETHICS

Cyber law and it's important

Cyber law refers to all the legal and regulatory aspects of Internet and World Wide Web.

It is important because for the following reasons:

i. It is required to overcome the cybercrime in the internet.

ii. It is important for the eradication of the illegal activities done in the internet.

iii. It touches all the aspects of transactions and activities on and concerning the internet and Cyberspace.

Digital Signature and it's important in the cyberspace

Digital Signature is the mathematical scheme for demonstrating the authenticity of a digital message or document.

It is important because it provides a legal framework to facilitate and safeguard electronic transactions in electric medium. It is also necessary to keep the uniformity standard and guarantee in all the activities of the e- sector.

Cybercrime

Cybercrime is defined as any type of illegal activity that makes use of the Internet, a private or public network, or an in-house computer system.

Telecommunication

Telecommunication is a system if transmission of sounds, images, texts or data in the form of electronic signals.

Computer ethics

Computer ethics is the branch of practical principles that deals with how the computer experts should make decisions in regard to the social and professional behavior. It is a set of moral principles that regulates the use of computers.

INTERNET AND SERVICES

Internet

The Internet can be described as an interconnection of several thousands of computers of different types belonging to various networks all over the world.

E-mail

E-mail is a message distributed by electronic means from one computer user to or more recipients via a network. It is the services of internet in which messages are sent from and received by the servers. E-mail has several advantages over conventional postal services.

Web Chat

Web chat is a program that enables you to communicate with others in real-time through messages. The user can log on to certain websites and communicate with various other users online by using Internet chat software. Chat software is interactive software that allows user to type comment in one window and receive replies in another from someone who is accessing the same software.

World Wide Web

World Wide Web is the leading information exchange service of the Internet. It gives users access to a vast array of documents that are connected to each other by the help of hypertext or hyperlink.

E-commerce

E-commerce is the commercial transactions conducted electrically on the Internet. It refers to a wide range of online business activities for products and services.

Internet telephony

Internet telephony can be defined as the technology that converts analog speech signals into digital signals and routes them through packet-switched networks of internet.

Video conferencing

Video conferencing means making communication between the users using sounds as well as pictures.

COMPUTER SECURITY

Computer security

Computer security refers to the protection of computer system and its valuable information against unwanted access, damage, modification or destruction.

Some computer hardware security measures

i) Regular maintenance

ii) Insurance

iii) Dust free

iv) Air condition system etc.

And some computer software security measures are as follows:

i) Password protection

ii) Backup system

iii) Defragmentation

iv) Scan disc

Hardware security

The protection of all hardware components used in computer system is known as hardware security. The computer equipment, software and data need to be protected from physical harm like fire, lightening, water, etc. as well as damage or theft, which is possible by hardware security which helps in protection of computer system.

Software security

Software security secure the data and software from getting lost and damaged and helps to insure privacy. It also protects data and software from the computer viruses. So, software security helps to prevent data loss.

Backup

Backup is a copy of a file which is used in the event of the original file being corrupted.

Password & good criteria for a strong password

A password is a secret word or phrase that gives a user access to a particular program or system. Any four good criteria for a strong password are as follows:

i. Do not keep a password which can be easily guessed such as date of birth, nickname, etc.
ii. Do not keep a password that is similar to your name or surname.
iii. Do not keep word as a password that is currently popular.
iv. Keep changing your password regularly.

Scandisk

Scandisk is a process, which involves in maintaining the disk files and folders using a kind of utility software.

Computer virus

Computer virus is a computer program that is designed to copy itself and infects or damages a computer without permission or knowledge of a user.

Voltage regulator

A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level.

Defragmentation

Defragmentation is the process of locating the noncontiguous fragments of data, rearranging the fragments and restoring the, into fewer fragments or into the whole file.

Fragmentation

The scattering of the parts of the same disk file over different locations is called fragmentation.

COMPUTER VIRUS

Computer virus

A computer virus is a type of computer program that can replicate itself by making copies of itself by making copies of itself without the user's knowledge or consent.

Computer virus spread from following ways

i. Opening the infected email attachment.

ii. By downloading infected programs from the internet.

iii. By using infected floppy disk, pen drives and CDs.

iv. By transferring an infected program over a network and executing it.

Type of computer virus

i) Boot Sector Virus

Boot Sector virus is regarded as one of the most hostile types of virus, a boot sector virus infects the boot record of a hard or a floppy disk. The virus moves the boot sector data to a different part of a disk. This virus allows the actual boot sector data to be read as though a normal start up were occurring.

ii) File Infecting Virus

This type of virus infects program files on a disk. When infected program is launched, the virus code is also launched. After the virus code has been launched, it will normal load and execute the program that has been infected.

iii) Multipartite Virus

This virus is the combination of parasitic and boot sector virus and due to this, it is able to infect both the files or boot sector of a disk. They infect program files and when it is executed, these viruses affect the boot record.

iv)Macro Virus

These viruses infect the Microsoft Office programs such as Excel, Word, Access and PowerPoint. When we open the Microsoft program then the virus is loaded and it affects the normal template or document. Since it is attached in the document, if the infected document is opened on other computer, it affects the computer too.

v) Script Virus

Script Virus is written in script programming languages, such as VBScript and JavaScript. It can infect a computer through various scripting environments, such as Windows Help, Windows installation files and Windows registry files.

The symptoms of computer viruses

i. Programs take long time to load.

ii. Renaming all the files with different names.

iii. Shows unusual error messages on the screen frequently.

iv. Corrupt or deletes system data and programs.\

Anti-virus software

Anti-virus software is a computer program designed to detect and remove viruses from the computer system.

Avoid the virus attacks

i. Scanning the email attachment before executing them.

ii. Use of a good anti-virus program to scan for viruses.

iii. Scanning the disk frequently for viruses.

iv. Not installing the pirated software, especially computer games.

The common characteristics of viruses are as follows:

a. Viruses slow down the system performance.

b. Viruses destroy data and programs from the system.

c. Viruses increase the size of executable files.

d. Viruses decrease the space on hard disk by duplicating files.

e. Viruses cause system to hang or freeze frequently

Worm is a program whose purpose is to duplicate itself. An effective worm will fill entire disk with the copies of itself and it can spread to multiple computer on network essentially clogging the entire system with copies.

Trojan horse is a destructive program that comes as an application. The software initially appears to perform a desirable function for the user prior to installation but steals and harms the system. Unlike viruses and worms, it does not replicate themselves.

A logic bomb infects a computer's memory but unlike a virus, it does not replicate itself. A logic bomb delivers its instructions when it is triggered by a specific condition, such as when a particular date or time is reached or when a combination of letter is typed on keyboard. It has the ability to erase a hard drive or delete certain files.

MULTIMEDIA AND ITS APPLICATION

Multimedia

Multimedia is a computer delivered electronic system which allows the user to control, combine, and manipulate different types of media. The media used in multimedia technology are text, sound, graphics, animation etc.

Multimedia is a system, which has the capability to integrate two or more types of media such as text, graphics, animation, audio and video. It also has the capabilities of getting input, digitizing, compressing, decompressing, storing, retrieving the data and information and demonstrating them in an interactive manner.

CD-ROM

CD-ROM is used to store data and information in the multimedia techonology. It's also called multimedia CD.

Virtual reality

Vitural reality techonology will enhace multimedia by supporting real time interactive, there dimensional graphics.

The hardware requirements for multimedia computer are as follows:

i. Larger storage devices

ii. Larger main memory.

iii. Sound card and speakers to play any audio associated with multimedia application

iv. Keyboard and pointing devices.

v. Faster CPU

Four multimedia softwares are as follows:

i. Windows Media Player

ii. Flash Player

iii. Adobe Photoshop

iv. Total Video Converter

The advantages of multimedia are as follows:

i. It increases learning effectiveness.

ii. It is portable.

iii. It cab store data and information for a long period of time.

iv. It makes presentation of the related subject matter attractive.

v. It makes teaching learning easier in the classroom.

MICROSOFT ACCESS

Data and Information

Data consists or raw facts and figures, Data consists of letter, sound, image or video within the computer.

Processed data is known as information. Using a data base program or software, they are converted into the meaningful result called information.

Database

A database is a collection of interrelated data. It refers to an organized collection of data stored on a computer in such a way that its content can easily be accessed, updated and queried upon with the help of a software program.

Example = Banks must have systems for keeping track of customers and their accounts.

Advantages of database

i. Database saves the data.

ii. Data can be stored in a small area or space in computerized database.

iii. Database protects from unauthorized access and use of data.

iv. It saves data from being lost.

Objects of MS Access

a. Table = Table are the core database object, used to store information. The tables are the containers for all the data in a database. In a table, data are arranged in a columns and rows.

b. Queries = Queries means to ask question about the data presented in the table. BY using queries, we can view records or data, modify the content of table and a lot more. It is a way of retrieving and editing information according to the condition asked. It is a strong tool using in searching of desired data from database.

c. Forms = A form is a database object used to enter and edit data in a table. Form can be used to edit the records of underlying tables or to enter new records.

d. Reports = A report is especially formatted collections of data organized according to our specification for summarizing and printing. They are the means to present the information as a printed document.

e. Macros = When macro is executed, it executes one or more database commands automatically. They are meant for automating the task that is done over and over again.

f. Modules = Modules are pieces of code used to impose particular behaviours to your application programmatically. They are more flexible and extensive than macros, although they are usually written for various and particular circumstances.

Attributes refer to a single data item related to a database object. The database schema associates one or more attributes with each database entity.

Record is a row of table in Microsoft Access. It contains information about a particular item stored in a table.

Database management system and its software

A database management system is a collection of programs that enables you to store, modify, and extract information from database.

Any four database management systems are as follows:

i. Relational Database Management System

ii. Hierarchical Database Management System

iii. Network Database Management System

iv. Object Oriented Database Management System

Field Data Type

A characteristic of a field that determines what kind of data it can store is known as Field Data Type.

Data types used in Ms-Access

a. Text = A text field contains up to 255 characters or it can set the length in the field size, text data type can include numbers letters and symbols.

b. Memo = This type of field holds an unlimited amount of text. It can accommodate 65, 535 characters.

c. Number = This type of field allows only the numbers to be entered.

d. Date/Time = This field type only allows date and time to be entered. It occupies 8 bytes.

e. Currency = This field allows to enter currency.

f. AutoNumber = This type automatically generates and insert the unique number in the new row.

g. Yes/No = It allows the user to select Yes or No when completing the field.

h. OLE object = It allows to link to binary data or files.

i. Hyperlink = It allows to create a hyperlink. It stores up to 64,000 characters.

j. Lookup Wizard = The lookup wizard creates a field that allows the user to choose a value from a list of values by using a list box or combo box.

Rules for naming field

a. It can be up to 64 characters long.

b. The naming cannot include control characters.

c. It cannot begin with leading spaces.

d. It can include any combination of letters, numbers, spaces and special characters except a period (.), an exclamation mark (!), an accent grave (`) and brackets ([ ]).

Primary Key

The primary key is a special column or group of columns in the table whose value must be unique in the table.

We can set the primary key by creating a table relationship. To relate tables a field is required which should be common to all the related tables. The common field of main table is known as primary key field.

A field property that controls what can be put into a field and how it can be placed there is known as field properties.

An input mask refers to a string expression that governs what a user is allowed to enter in as input in a text box.

Validation rule is a property of Date/time field.

The differences between primary key and foreign key

Primary Key	Foreign Key
It is a column or a set of column that can be used to uniquely identify a row in a table.	It is a column or a set of column that refer to a primary key or a candidate key of another table.
A table can have a single primary key that can reference different tables.	A table can have multiple foreign key that can reference different tables.

Field property: A field property that controls what can be put into a field and how it can be placed there is known as field properties.

Validatation Rule: Validation rule is a property of Date/time field.

Input Mask: An input mask refers to a string expression that governs what a user is allowed to enter in as input in a text box.

Relational Database management system: A relational Database management system is a database system that is based on relation model. It is a database management system designed to manage a relational database.

Sorting records: Sorting records is the arrangement of records on the basis of a field or fields of a table either in ascending order or in descending order.

Filtering records

Filtering records is the process of viewing required data of a table that specify the specified criteria.

The different techniques for filtering records are as follows:

i. Filter by selection

ii. Filter by form

iii. Advanced filter

QUERYING DATABASE

Microsoft Access Query

Query is a way of extracting information from a database, usually by using certain criteria or requesting certain data. It is request for database records that fit specified criteria.

Uses of query

i. A query can count the amount of records that meet the certain criteria.

ii. It can also be used to extract data to a separate table or delete data, change data and many other things.

Dynaset

A dynaset is a set of data that is dynamically linked back to the database. Instead of having the query result stored in a temporary table, where the data cannot be updated directly by the user, the dynaset allows the user to view and update the data contained in the dynaset.

Types of queries

a. Select query = It is a query in which the relevant data from a table is selected and displayed. It allows the user to retrieve data from one or more tables and displays the results in a datasheet where the user can update the record.

b. Parameter queries = It is a query that when run displays its own dialog box prompting the user for information, such as criteria for retrieving records or value the user want to insert in a field.

c. Crosstab queries = A query that calculates a sum, average, count, or other type of total for data that is grouped by the two types of information is known as crosstab queries.

d. Action queries = A query which performs an action with the records /fields selected by the query. Action queries includes delete, Append, update and make table queries.

Differences between filter and Select query

Filter	Query
A filter cannot be saved as separate object.	A query can be saved as separate object.
A filter cannot be used for displaying the records of more than related table at once.	A query can be used for displaying the records of more than related table at once.
A filter cannot be used for performing calculation on values of numeric fields.	A query can be used for performing calculation on values of numeric fields.

Queries are used

a. Update data, delete records or append new records to a table.

b. Create a new table with records from one or more tables.

c. view data form multiple tables sorted in a specific order.

d. Find and display duplicate or unmatched records.

FORMS

Form object

Form object is an interface that allows the user to input, edit or view data from/in your database.

To create a form for a table using Form wizard, following steps should be taken.

Step

1. In the database window, click Form tab under objects.

2. Click the New button on the database window toolbar.

3. In the New Form dialog box, click on the form wizard option.

4. Click the name of the table that you want to base your form on.

5. Click OK to open the first Form Wizard dialog.

6. Click >> to add the required or all the fields from the selected table and click on Next.

7. Choose a layout and Click Next.

8. Click on the style that you want to apply for the form and click next.

9. Name the form.

10. Click Finish.

REVIEW OF CONTROL STRUCTURE

Control flow structure and basic control structure of QBASIC

Control flow structure is instructions, statements or group of statements in a programming language which determines the sequence of execution of other instructions or statements.

The basic control structures of QBASIC are as follows:

I. Sequential Structure II. Loop Structure III. Selection Structure

Loop structure and it's importance of loop in programming

A loop structure is a logic, which is used to execute one or more than one statement for a number of times.

Loop in a program allows for repeated iteration over the same set of instructions. Depending on the type of loop and the constraints will depend on how many times those instruction get repeated.

Infinite loop

Never terminating loop is called Infinite loop. Pressing "Ctrl + Break" or "Ctrl + C" keys breaks the infinite loop.

Counter or control variable

Counter is a program which is used when one needs to count how many times a program executes a loop.

key to remember

i. Server = A computer that provides the facilities of sharing the data, software, and hardware resources on the network is known as server.

ii. Workstation = Workstation refers to the computers that are attached to a network and use the resources of the network.

iii. Network Interface Card = Network adaptor is the interface that is used for connecting computers in networks. It is commonly known as Network Interface Card (NIC).

iv. Transmission Media = The communication channel provides the physical path through which data, information flow on a network.

The differences between dedicated server and non-dedicated server are as follows:

Dedicated Server	Non-dedicated Server
Dedicated Server means the server will only do what the user want it to do. The user has all of the computer resources at command.	A non-dedicated server is where the resources are shared between multiple users.
A dedicated server is a server shoes only job is to help workstation access data, software and hardware.	A non-dedicated server acts as a server as well as a workstation.
For example = If you are referring to a game server then dedicated is when your computer just runs the server.	For example = If you are referring to a game server then non-dedicated is when you are the server and you play.

FTP = File Transfer Protocol

SMTP = Simple Mail Transfer Protocol

TCP/IP = Transmission Control Protocol/ Internet Protocol

ISP = Internet Service Provider

POP = Post Office Protocol

UTP = Unshielded Twisted Pair

STP = Shielded Twisted Pair

NetBEUI = Net Bios Enhancer User Interface

DARPA = Defence Advanced Research Projects Agency

HTTP = Hyper Text Transfer Protocol

four communication protocols are as follows:

i. Transmission Control Protocol/ Internet Protocol (TCP/IP)

ii. Post Office Protocol (POP)

iii. Net Bios Enhancer User Interface (NetBEUI)

iv. Internet Pack Exchange/ Sequential Packet Exchange (IPX/SPX)

The facilities provided by the internet are as follows:

i. Electronic Mail (E-mail) = It is an electronic message sent from one computer to another.

ii. Telnet = Telnet allows internet users to access another computer linked to the internet.

iii. Usenet = Usenet is acting like a huge bulletin board with thousands of newsgroups and subgroups.

Internet	Intranet
It is an open, public space, a worldwide system of interconnected computer networks.	It is a private network within an organization that resembles the internet.
It is worldwide, publicly accessible series of computer networks.	It is password protected and is accessible to only the authorized persons.