---
title: "Data versus signal"
subject: "Data Communication"
chapter: 1
key: "semester_5/data_communication:data-vs-signal"
source: https://www.bctengineer.com/q/semester_5/data_communication/data-vs-signal
site: BCT Engineering
---

# Data versus signal

Data Communication · Chapter 1: Introduction

- Asked in: 2078 Kartik, 5 marks
- Video: [Signals | Analog & Digital |  Data Communication | Lec-03 | Bhanu Priya](https://www.youtube.com/watch?v=6CyXtvOfm4g) — Education 4u
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/data-vs-signal
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-1

## Question

Differentiate data and signal with two examples of each.

## Short answer

Data is raw abstract information like voice or text; a signal is its physical representation such as a varying voltage or digital pulses for transmission. Data and signal types are independent.

## Answer

**Data** is raw information in a form that is stored or processed. **A signal** is the electrical, optical or electromagnetic representation of data used to carry it over a medium. Data is turned into a signal before transmission.

| Point | Data | Signal |
|---|---|---|
| Meaning | Entity that carries information | Physical wave that carries data |
| Form | Analog or digital values | Analog or digital waveform |
| Where used | Stored and processed in the computer | Transmitted on the channel |
| Nature | Abstract, not tied to a medium | Electrical/optical/EM; has amplitude, frequency, phase |
| Conversion | Encoded into a signal by the transmitter | Decoded back into data by the receiver |

#### Examples
- **Analog data**: voice, temperature readings. **Digital data**: text in ASCII, a stored file of 0s and 1s.
- **Analog signal**: the varying voltage of a telephone line (or an AM wave). **Digital signal**: the +5 V / 0 V pulse train on a computer bus, or the Manchester-coded pulses on Ethernet.

A digitised voice (digital data) can be sent on an analog signal using a modem, so the data type and the signal type are independent.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the relationship between data and signal?
   A. Signal is stored in computer, data travels on channel
   B. They are identical
   C. Signals are always analog and data digital
   D. Data is converted to a signal for transmission
   Answer: D. A signal is the physical representation that carries data over the medium. (Key point: Definition)

2. Can digital data be sent on an analog signal?
   A. Yes, using a modem
   B. No, never
   C. Only in fibre
   D. Only after conversion to analog data
   Answer: A. Data type and signal type are independent. (Key point: Independence)

3. Which is digital data?
   A. Voice
   B. Text in ASCII
   C. Temperature readings
   D. Telephone line voltage
   Answer: B. Voice and temperature are analog data; the voltage is a signal. (Key point: Example)

4. Which describes a signal?
   A. An abstract entity not tied to a medium
   B. A stored file
   C. A physical wave with amplitude, frequency and phase
   D. A character code
   Answer: C. Data is abstract; a signal is electrical/optical/EM. (Key point: Signal properties)

## Related in Data Communication

- [Even and odd parts of a signal](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aeven-odd-parts) — Data Communication, chapter 2
- [Fourier transform of a DC signal](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aft-dc-signal) — Data Communication, chapter 3
- [Plotting line spectra of a CT signal](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-spectrum-plot) — Data Communication, chapter 3
- [Why band-limit a signal before sampling](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Asampling-bandlimit) — Data Communication, chapter 5
- [Short note: STP versus UTP](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Autp-vs-stp) — Data Communication, chapter 4, asked 2×
- [Short note: Optical fiber versus STP](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aoptical-fiber-vs-stp) — Data Communication, chapter 4

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