1. Data Representation in a Computer - Introduction

Data Representation refers to the methods used internally to represent information stored in a computer. Computers store lots of different types of information:

• Text (this refers to letters, numbers and symbols)
• Graphics (such as pictures, drawings and clip art)
• Sound (voice data)
• Instructions (computer commands)

At least, these all seem different to us. However, ALL types of information stored in a computer are stored internally in the same simple format: a sequence of 0's and 1's. How can a sequence of 0's and 1's represent things as diverse as your photograph, your favorite song, a recent movie, and your term paper?

It sounds complicated. However you should understand that computers don’t understand our natural languages like Kiswahili, English or Kalenjin. They have their own language called machine language. This means, what you type or speak into the computer data is converted into a language that computers are able to understand.

In digital computers, the user input is first converted and transmitted as electrical pulses that can be represented by two distinct states ON and OFF or ‘1’ and ‘0’ respectively. The sequence of ‘1’ and ‘0’ forms electrical signals that the computer can understand; the figure below shows the difference between a discrete signal (digital) and a continuous (analogue) signal

A digital signal

refers to an electrical signal that is converted into a pattern of bits. Unlike an analogue signal, which is a continuous signal that contains time-varying quantities, a digital signal has a discrete value at each sampling point. The precision of the signal is determined by how many samples are recorded per unit of time.

Parameters used with signals

AMPLITUDE (A)

this is the maximum displacement that the waveform of an electrical signal can attain

FREQUENCY (f)

this is the number of cycles made by the electrical signal in one second. Its measured in hertz (Hz) 1 cycle per second F=1/t

Periodic time (T)

Periodic time is the number of unit time per cycle and can be calculated as reciprocal of frequency i.e T=1/f

When a digital signal is to be sent over analogue telephone lines e.g email, it has to be converted to analogue signal . this is possible with the use of a device called the Modem derived from the words Modulation and Demodulation. Modulation stands for converting a digital signal to analogue and demodulation refers to converting an analogue signal to digital

Topical Questions

1. Briefly explain how data is represented in a computer

2. With the aid of a well labelled diagram, distinguish between analogue and digital signals

3. Define:

i. Amplitude

ii. Frequency

iii Periodic time

Guide

Free Mathematics paper 1 questions and answers - Click Here

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