Chapter – 3 [Data Communication]-Notes

Q. What is DATA? What are the Types of DATA?

Data

• The collection of raw facts and figures is called data.

Types of data:

• Text
• Numeric
• Image
• Audio
• Video

Text:

• Text consists of words, sentences and paragraphs.
• Text is stored in the form of ASCII codes.
• ASCII stands for American Standard Code for Information Interchange and it is a seven-bit coding scheme for computers.
• Text Processing: It refers to the ability to manipulate words, lines and pages.

Numeric:

• Numeric data consists of digits from 0 to 9.
• It can be positive or negative number.
• There are two types of numeric data
• Integers (+56, -90 etc.)
• Real (2.34, -8.97 etc.)

Image:

• Image consists of charts, graphs, pictures and free hand drawings.
• The data is transferred in the form of 8 bits pattern.

Audio:

• Sound is a representation of audio.
• Sound is converted into digital code by sampling the sound waves 44056 times per second.
• Each sample is converted into a 16 bit number.

Video:

• It is produced by camera.
• It is a combination of images and it conveys the idea of motion.
• It creates actions and movements.

Q. What is Data Communication? What are the components of Data Communication?

Data Communication:

• Data communication is the exchange of data between two devices via some form of transmission media

or

• Data communication is the transfer of data or information from one location to another.

or

• The movement of encoded information by means of an electrical transmission system from one computer or device to another computer or device through communication channels.
• In this process, data is transmitted electronically from one system to another system using standard methods.

Components of Data Communication:

There are five components of data communication.

• Message
• Sender
• Receiver
• Communication channel
• Encoder and Decoder

Message:

• The message is the information or data to be communicated.
• Message can be text, numbers, pictures, sound, video or any combination of these.

Sender:

• The sender is the device that sends the data.
• It is also called a source or transmitter.
• It can be a computer, telephone, camera, or so on.

Receiver:

• The receiver is the device that receives the data.
• It is also called destination or sink.
• It can be a computer, telephone, TV, or so on.

Communication channel:

• It is a path by which data travels from sender to receiver.
• There are two types of communication channels.
• Guided Media (Cables-twisted pair, Coaxial, fiber optic)
• Unguided Media (Microwave, satellite)

Encoder and Decoder:

• The encoder converts the digital signal to a form that can pass through the transmission medium.
• Decoder converts signals from encoded form to a digital form understandable for the receiver.
• Sender and received cannot communicate without an encoder and decoder.

Q3. What are Signals? What are the Types of Signals?

Signals:

• The electromagnetic or light waves representing data are called signals
• There are two forms of signals.

• Analog Signals.
• Digital Signals.

Analog Signals:

• These are continuous electrical signals in the form of waves.
• This wave is called a carrier wave.
• In analog signals, the transmitted power varies over a continuous range e.g. sound, light, and radio waves.
• There are two characteristics of analog signals

Frequency:

A number of times a wave repeats during a specific time. It is measured in hertz (Hz).

Amplitude:

It is the height of a wave within a given period of time.

Digital Signal:

• A digital signal uses on-off electrical pulses in discontinuous or discrete form.
• It is a sequence of voltage pulses represented in binary form. Binary means two digits 0 and 1. Each binary digit is called a bit and it is the smallest element of data.
• Computers process the data in the form of digital signals because it works with binary numbers.
• An electrical pulse inside the computer is represented by 1 and the absence of an electrical pulse is represented by 0.

Q. What is the asynchronous and synchronous transmission? Differentiate between them.

• Data may be sent by asynchronous or synchronous transmission

Synchronous

• Synchronous transmission allows the data to be sent in the form of blocks or frames. It is more efficient than asynchronous transmission.

Asynchronous

• In asynchronous transmission, data is sent in form of bytes or characters. In this transmission start (0) bits and stop (1) bits are added with data.