2. Concepts of Data Representation in Digital Computers

Platforms that data must go through to communicate with hardware

Data and instructions cannot be entered and processed directly into computers using human language. Any type of data, be it numbers, letters, special symbols, sounds or pictures must first be converted into machine readable form. Due to this reason, it is important to understand how a computer together with its peripheral devices handle data in its electronic circuits. On magnetic media and in optical devices.

Data representation in digital circuits

In digital circuits, when the circuit is ‘on’, its interpreted as a ‘1’ and when ‘off’ its interpreted as a ‘0’. These ‘1s’ and ‘0s’ is what computers understand and its refered to as binary language.

Data representation in magnetic media

The presence of a magnetic field in one direction magnet media is interpreted as ‘1’, while the field in the opposite direction is interpreted as ‘0’. Magnetic technology is mostly used on storage devices which are coated with special magnetic materials such as iron oxide. Data is written on the media by arranging the magnetic dipoles of some iron oxide particles to face in the same direction and some others in the opposite direction.

Data representation on optical media

In optical devices, the presence of light is interpreted as ‘1’ while its absence is interpreted as ‘0’. Optical devices use this technology to read or store data. Take an example of a CD-ROM. If the shiny surface is placed under a powerful microscope, the surface can be observed to have very tiny holes called pits. The areas that do not have pits are called land. Land reflects laser light that hits on the surface but bits don’t reflect. The reflected pattern of light from the rotating disk falls on a receiving photoelectric detector that transforms the patterns into digital form.

Reasons for use of binary system in computers

Binary systems are:

1. Reliable

2. Occupy less space

3. Use less energy

Bits, bytes, nibble and word

Bits: a bit can be defined as a binary digit which can either be 0 or 1. It is the basic unit of data or information in digital computers.

Byte: a group of bits (often 8) used to represent a character is called a byte. A byte is used to measure the memory of a computer

A nibble: half a byte, which is usually a grouping of 4 bits

Word: two or more bytes make a word

Word length: measure of the number of bits in each word

Example: let 11110000 represent a binary figure

There are 8 bits in the figure. Count

These 8 figures make up a byte

1111 or 0000 is a nibble this is because they are 4 of the 8 figures thus half

11110000 and 11110000 are two figures thus a word

11110000 and 11110000 make a word that has 16 bits thus word length

Questions

1. Why is the binary number system used in data representation?

2. Explain the following terminologies as used with data representation:

a) Word

b) Nibble

c) Byte

d) Bit

e) Word length

3. Define the following words

a) Amplitude

b) Frequency

c) Periodic time

4. Explain the role of a modem in communication

5. Using a diagram illustration, explain how data is represented in:

a) electronic circuits

b) magnetic media

c) CD-ROM

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