1.1 Digital and Analog Systems

1.

Digital and analog system classification is based upon the type of signals used in the system.

	a)	An Analog signal represents continuous values but a digital signal can only represents discrete values.
	b)	For example, if a signal varies in magnitude between 0 volts and 5 volts,

		The analog system can take any value between 0 and 5.
		But the digital system can take for example any value of the discrete values of 0, 1, 2, 3, 4 and 5.
		If a signal in such digital system has the value 4.2 at any instant of time, it is represented by the nearest discrete value (4, in this case). All signals ranging from 3 to 3.5 would be represented by 3 and all signals ranging from 3.5 to 4 would be represented by 4.

2.

Modern computers and communications are considered as digital systems.

	a)	Such systems are binary systems with signals represented by only two values - zero or one.
	b)	For example, in an audio digital system, audio data is converted to a series of 1s and 0s. Such binary format is represented by digital signals handled by the system.

1.1 Digital and Analog Systems

3.

Both analog and digital systems have their advantages and disadvantages.

a)

Noise

		Analog systems make efficient use of bandwidth and are relatively resistant to noise.
		Digital systems are greatly affected by noise.

b)

Flexibility

		Analog systems are less flexible to changes in design since they are implemented with hardware components and are not usually flexible to changes in parameters of input signals. Any change in input parameters of analog system may require a new circuit design and implementation.
		Digital systems on the other hand, are very flexible to changes in design. This flexibility in changes is considered as the main advantage with digital systems since they are built using programmable components and standardized circuits. Thus, a digital component can be reused to meet new design requirements just by modifying the way it is programmed.