COMPILED BY: MISS SHABINA MUSHTAQUE
ASSIGNMENT # 1
Student Name : Javeria Mughal
Student Roll num : 18b–119-se (A)
CHAPTER 1
Introduction
Data communications
The word data refers to information presented in whatever form is agreed upon by the parties creating and
using the data. Data communications are the exchange of data between two devices via some form of
transmission medium such as a wire cable. For data communications to occur, the communicating devices
must be part of a communication system made up of a combination of hardware (physical equipment) and
software (programs).
The effectiveness of a data communications system depends on four fundamental characteristics: delivery,
accuracy, timeliness, and jitter.
I. Delivery. The system must deliver data to the correct destination. Data must be received by the
intended device or user and only by that device or user.
II. Accuracy. The system must deliver the data accurately. Data that have been altered in transmission
and left uncorrected are unusable.
III. Timeliness. The system must deliver data in a timely manner. Data delivered late are useless. In the
case of video and audio, timely delivery means delivering data as they are produced, in the same
order that they are produced, and without significant delay. This kind of delivery is called real-time
transmission.
IV. Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of
audio or video packets.
Provide any example OF DATA COMMUNICATION holding all four characteristics
_There are so many examples of data communication like computer
networking ,telecommunication and radio/satellite communication. The
most comman example of data communication is when a computer is
connected to the internet via a WiFi connection or a a cable which uses
a wirless medium to send and receive data from one or more remote
servers.
Data communications components
1. Message. The message is the information (data) to be communicated. Popular forms of information
include text, numbers, pictures, audio, and video.
2. Sender. The sender is the device that sends the data message. It can be a computer, workstation,
telephone handset, video camera, and so on.
3. Receiver. The receiver is the device that receives the message. It can be a computer, workstation,
telephone handset, television, and so on.
4. Transmission medium. The transmission medium is the physical path by which a message travels from
sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable,
fiberoptic cable, and radio waves.
5. Protocol. A protocol is a set of rules that govern data communications. It represents an agreement
between the communicating devices.
Data Representation
Information today comes in different forms such as text, numbers, images, audio, and video.
Provide detail of each form of data:
Text
In data communications, text is represented as a bit pattern, a sequence
of bits (Os or 1s). Different sets of bit patterns have been designed to
represent text symbols. Each set is called a code, and the process of
representing symbols is called coding. Today, the prevalent coding system
is called Unicode, which uses 32 bits to represent a symbol or
character used in any language in the world. The American Standard
Code for Information Interchange (ASCII), developed some decades ago
in the United States, now constitutes the first 127 characters in Unicode
and is also referred to as Basic Latin.
Numbers:
Numbers are also represented by bit patterns. However, a code such as
ASCII is not used to represent numbers; the number is directly converted
to a binary number to simplify mathematical operations.
Images:
Images are also represented by bit patterns. In its simplest form, an
image is composed of a matrix of pixels (picture elements), where each
pixel is a small dot. The size of the pixel depends on the resolution. For
example, an image can be divided into 1000 pixels or 10,000 pixels. In the
second case, there is a better representation of the image (better
resolution), but more memory is needed to store the image.
After an image is divided into pixels, each pixel is assigned a bit pattern.
The size
and the value of the pattern depend on the image. For an image made of
only black-and-white dots (e.g., a chessboard), a I-bit pattern is enough
to represent a pixel.
If an image is not made of pure white and pure black pixels, you can
increase the size of the bit pattern to include gray scale. For example, to
show four levels of gray scale, you can use 2-bit patterns. A black pixel
can be represented by 00, a dark gray pixel by 01, a light gray pixel by 10,
and a white pixel by 11. There are several methods to represent color
images. One method is called RGB,so called because each color is made
of a combination of three primary colors: red,green, and blue. The
intensity of each color is measured, and a bit pattern is assigned to
it. Another method is called YCM, in which a color is made of a
combination of three other primary colors: yellow, cyan, and magenta.
Audio
Audio refers to the recording or broadcasting of sound or music. Audio is
by nature different from text, numbers, or images. It is continuous, not
discrete. Even when we use a microphone to change voice or music to an
