Know and understand the need to convert analogue to digital data so it can be processed by a computer

Types and Components of Computer Systems

Objective

Know and understand the need to convert analogue to digital data so it can be processed by a computer.

1. Why Convert Analogue Data?

Computers operate using binary (digital) signals. Most real‑world information – sound, light, temperature, pressure – is analogue. To store, manipulate, or transmit this information with a computer, it must be transformed into a digital form that the computer can understand.

2. Analogue vs. Digital

3. The Analogue‑to‑Digital Conversion Process

The conversion is performed in three main stages:

1. Sampling – measuring the analogue signal at regular time intervals.
2. Quantisation – assigning each sampled value to the nearest value from a finite set.
3. Encoding – representing the quantised values as binary numbers.

4. Sampling

Sampling rate (or frequency) determines how many samples are taken per second. According to the Nyquist theorem, the sampling rate must be at least twice the highest frequency component of the analogue signal to avoid aliasing.

\$f{s} \ge 2 f{max}\$

where f_s is the sampling frequency and f_max is the maximum frequency present in the analogue signal.

5. Quantisation

Quantisation maps each sampled amplitude to a discrete level. The number of levels is determined by the bit depth (number of bits per sample).

Number of levels = \$2^{n}\$, where \$n\$ is the bit depth.

Example: an 8‑bit system provides \$2^{8}=256\$ possible levels.

6. Encoding

Each quantised level is expressed as a binary code. For an 8‑bit system, a level of 173 would be encoded as 10101101.

7. Example: Converting a Simple Audio Signal

Consider a 1‑kHz sine wave sampled at 8 kHz with a 4‑bit depth.

• Sampling interval = \$\frac{1}{8000}\,\text{s}=125\,\mu\text{s}\$.
• Maximum amplitude is mapped to 15 (binary 1111), minimum to 0 (0000).
• Each sample is stored as a 4‑bit binary number, producing a digital representation of the original sound.

8. Benefits of Digital Data

• Easy to store, copy and retrieve without degradation.
• Supports error detection and correction.
• Facilitates fast processing and complex calculations.
• Enables compression, encryption and efficient transmission.

9. Summary

Analogue data must be converted to digital form for computer processing. The conversion involves sampling the continuous signal, quantising the sampled values to a limited set of levels, and encoding those levels as binary numbers. Understanding this process is essential for working with multimedia, sensors, and any real‑world data in ICT.