1. Data Representation and Number Systems

1.0 Introduction.

All data in a digital computer is stored as electronic signals, either voltages or currents. These electronic signals are used to represent other data types such as numbers or letters or other items. In most digital computers systems the electronic signals can only handle two signal levels represented by a digit 0 and a digit 1, namely high or low. These values are also known as, 1 or 0, ON or OFF, SET or RESET or TRUE or FALSE.

1.1 Digital signals.

A microprocessor system operates on digital signals. Digital signals are represented by two discrete voltage levels or states which are often known as either ‘high’ (5 V) or ‘low’ (0 V) with respect to each other. The high state is often known as a logic one ( 1) and the low known as a logic ( 0 ).

1.2 Data transmission.

The bus in a microprocessor system transmit data in parallel form.
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Figure : 1

Data can also be transmitted in serial form
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Figure : 2

1. Decimal Number

In everyday situations, a system of counting using a base of ten is employed. This is known as a decimal system, and its main justification for use is often quoted as being that human beings have ten fingers with which to count.
A decimal number is composed of one or more digits chosen from a set of ten digits {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
Base number is 10.
The weights are all multiples of 10.

Example: 3 5 7 ----- digits

102 101 100 ----- weights as powers of 10

100 10 1 ----- actual weight value __________________ 300 50 7 ----- components of number

= 357
1. Binary Number

A decimal system is not particularly suitable for direct use in electronic circuits. Due to practical limitations imposed by electronic devices, only two conditions are consistently