Data and signal (Analogue & Digital)

What is Difference between Data and signal?

There is difference between Data and signal & the important points are given below:-

1The Entities which convey meaning within computer or computer system.These are the electromagnetic or electric which used to first encode & transmit data.
2It is usually referred as the unprocessed or raw data.
When data are converted into electromagnetic signal which is then ready to be sent from one device to another device.
3The values of data can be either represents qualitative or quantitative variables.Naturally it can be in form of either analogue or digital.

“What we want to send is known as Data and what we can send through the medium is known as Signal”

Analogue & Digital

What is Difference between Analogue & Digital?

1A data can be analogue or digital.A data can be analogue or digital.
2It is a continuous waveform e.g. music, voice & etc.
It is non-continuous or discrete waveform.
3The values of data can be either represents qualitative or quantitative variables.The data which may be in form of letters, numbers or set of characters.
4It is represented by sine waves.It is represented by square waves.
5Figure A showing the example of Analogue.Figure B showing the example of Analogue.
Figure A
Figure B

Periodic and Non-Periodic signals

Both analogue and digital signal can be either periodic or non-periodic signal. The signals which completes its each cycle in a specific time period, a signal which tend to repeat its previous cycle is known as periodic function. We can also say that this signal is predictable. While on other hand the other the non-periodic signal is a signal which do not follow its previous signal. A signal which does not complete each in a specific interval of time is known as non- periodic signal. This signal is also known as non-predictable signal.

Note: periodic signal is preferred on non-periodic signal because in periodic signal is the output is already known and everything which is our control is supposed to be good.

Analogue signals

Here we will discuss some properties of the analogue signals. These properties are related to periodic analogue waves. It includes following important points which are given below:-

  1. Peak amplitude
  2. Period
  3. Frequency
  4. Phase
  5. Time and frequency domains
  6. Bandwidth

We discuss all these properties with respect to sine wave. As we know sin wave is a periodic wave.

(1) Peak amplitude

Peak amplitude of sine wave is the highest amplitude or the highest value of the sine wave. Sine wave x-axis indicates the time and y-axis represents amplitude. Amplitude of the wave can be anything like voltage or current. The highest value of this axis is the peak of the wave. The figure a showing results of Peak Amplitude is as under.

Peak amplitude
Peak Amplitude

(2) Period

It is usually referred as the time taken by the signal to complete its one cycle (Time should be in seconds). Period is represented by T and its formula is

T α 1÷f

Whereas T is the time and f representing frequency.


Here crust means the positive maximum amplitude and trough means the negative maximum amplitude & wavelength is the distance between two adjacent crusts or troughs.  

(3) Frequency

It means that number of periods completed in one (1) second by a signal. The concept of frequency is very important to understand which used in many different places. If the frequency of the signal is high it means the wave completing more periods in one (1) second.


On other hand, the higher frequency means the wavelength of any frequency is low. The unit of frequency is hertz (Hz). The relation of wavelength and frequency is inverse as well as increasing in one value which decreases other.

                      F α 1÷λ

And the relation between time period and frequency

                    F α 1÷T

(4) Phase

Phase of the wave usually refers to position of the wave relating it to the origin point. For example the phase of sinusoidal wave is zero when it is starting from the origin point.


As we can see there is a phase change of ¼ cycles in the wave. The original wave is starting from zero position and when we delay it by ¼ cycles or when we delay the wave by 90 degrees the phase of wave changes.

Note: delay in function causes it to move to the left side of time axis and forwarding the value causes our value to move in right side of the time axis.

(5) Time and frequency domains

The x-axis is independent and we take time on that axis. This means over time is independent of everything. This is called time domain. Time is independent and every other thing which is on y-axis is dependent whether we take current, voltage or any other parameter. The change in time do not depend on any other thing. And when we discuss about frequency domain we replace time with frequency now we have frequency on x-axis and it is now independent the representation of frequency domain and time domain changes and the graphical representation also changes.

Time & Frequency domains
Time & Frequency

In frequency domain we have a continuous signal because the time is changing and in frequency domain we have only one value so we have one straight line of specific amplitude.

(6) Bandwidth

Bandwidth is the combination of different signals in frequency domain. The formula of bandwidth is as under.

B.W = F(max) – F(min)

The combination of different frequencies form a spectrum which makes a band of frequencies.


As the bandwidth is the combination of different waves so the amplitude of each signal differs from the other.

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