Data Representation in a Computer
To define data and information
Introduction Data refers to a collection of raw facts, figures or instructions that do not have much meaning to the user Information refers to data which has been manipulated into a more meaningful form Information is stored in a computer inform of binary digits(bits) which takes two states i.e. either 1(on) or 0(off). Computers use binary digits to represent everything. That means that whatever you store in a computer must be expressed as a binary pattern of ones and zeros. Take a simple integer, 27. In binary code, this number is actually 110112, each digit referring to a power of two
To define various terms used in data representation
To describe various types of signals
It is the voltage level in a circuit which represents the flow of data Signals can either be analog or digital in nature
ANALOG SIGNAL
It is a signal made up of a continuous varying waveform It rises to +1 and falls to -1 in a continuous manner
DIGITAL SIGNAL
It is made up of a non-continuous discrete signal
A wave is described using the following terms
Amplitude (A); It is the maximum displacement that an electrical signal can attain. In the above example the amplitude is one.
Frequency (F); It is the number of cycles made by a signal per second i.e. how many waves per second. It may be measured in: Hertz 1 Hz means 1 wave per second, Kilohertz 1 kHz is 1,000 waves per second, Megahertz 1 MHz is 1 million waves per second. Gigahertz1 GHz is 1,000 million waves per second.
Periodic Time; It is the time taken for one complete oscillation.
Wavelength; means the length of one wave i.e. the distance from any point on a wave to the same point on the next cycle of the wave. It can be measured in Km, m , cm, e.t.c
DATA REPRESENTATION ON A TELEPHONE LINE
Digital signals are unable to travel across traditional analogue telephone wires. To transmit digital signals across telephone lines, the signals need to be converted to analogue signals. Signal modulation is the conversion of digital signals to analog signals for transmission over analog media. Signal demodulation is the conversion of analog signals back to digital signals on the receiving end. Signal modulation and demodulation is performed using a device known as modem. It is a modulator and demodulator i.e. it convert digital signals to analog signals for transmission over telephone lines. On the receiving end it converts the analog signals back to digital signals.