IGCSE · Practice questions · Serial and parallel, simplex, half-duplex and full-duplex

Match the method to the job.

Six original Cambridge-style questions on methods of data transmission, with mark-point solutions.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Two choices, two reasons.

Serial: one bit at a time, one wire, long distances, no skew.
Parallel: several bits at once, several wires, fast but short distances only (skew).
Direction: simplex one way; half-duplex both ways in turn; full-duplex both ways at once.
Scenario questions: name both parts and link each reason to the scenario.

Explain

[2 marks]

Describe how data is transmitted using parallel data transmission.

Several bits are sent at the same time. ✓
Using several wires (one wire per bit). ✓

Explain

[3 marks]

Give one advantage and two disadvantages of parallel transmission compared with serial transmission.

Advantage: faster over short distances because several bits are sent at once. ✓
Disadvantage: data can be skewed (bits arrive at different times) over long distances. ✓
Disadvantage: needs more wires so is more expensive; wires can interfere with each other. ✓

Recall

[3 marks]

Describe the difference between simplex, half-duplex and full-duplex data transmission.

Simplex: data is sent in one direction only. ✓
Half-duplex: data is sent in both directions, but only one direction at a time. ✓
Full-duplex: data is sent in both directions at the same time. ✓

Apply

[4 marks]

A school sends files from a server to a printer 80 metres away. The printer sends status messages back, such as "out of paper", but never while it is receiving a file. Identify the most suitable transmission method and justify your choice.

Serial. ✓
Because 80 m is a long distance and parallel data would suffer from skew. ✓
Half-duplex. ✓
Because data must travel both ways, but not at the same time. ✓

Apply

[2 marks]

Explain why full-duplex transmission is used for an online multiplayer game.

The player's moves must be sent to the server at the same time as game updates are received. ✓
Full-duplex allows data in both directions simultaneously, so there is no waiting / less lag. ✓

Analysis

[2 marks]

A student says: "Parallel transmission is always better because it is faster." Evaluate this statement.

It is faster only over short distances, such as inside a computer. ✓
Over long distances skew corrupts the data, so serial is better (and cheaper, with fewer wires). ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.