← IGCSE Computer Science Paper 1

Full-duplex data transmission

Data is sent in both directions at the same time, so both devices can send and receive at once, for example during a telephone call or over a broadband connection.

Part of: IGCSE Computer Science 0478 — 2.1 Data Transmission Types and Methods — Module 30, WA Computer Science ATAR Year 11 — Network Communications — Module 22

Understanding Full-duplex data transmission in IGCSE Computer Science Paper 1

What it does: The double-headed arrow shows data flowing in both directions simultaneously, which is full-duplex. On a phone call both people can talk and hear at the same time. A remote control only sends data one way (simplex). Taking turns describes half-duplex. Full-duplex allows sending and receiving at the same time. One-way only transmission is simplex, not full-duplex.

Common mistakes: Simplex sends data in one direction only. Both devices sending and receiving at the same time is full-duplex, so the line should be mode = "full-duplex". Half-duplex only lets data go both ways one direction at a time. A telephone call lets both people talk and hear at once, so it is full-duplex.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Full-duplex data transmission to a class →

This module's key terms are also in a printable crossword (Modules 131–141) and word search (Modules 121–141).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning
Duo
Which description matches full-duplex transmission?
Data travels in both directions at the same timeData travels in one direction only
Matches
Full-duplex: data goes one way only, like a TV broadcast
↓
This describes simplex transmission. Full-duplex sends data in both directions at the same time.
Applying
Meanings
Term
full-duplex
Meaning
Data is sent in both directions at the same time, so both devices can send and receive at once, for example during a telephone call or over a broadband connection.
Practice
// Full-duplex telephone call
Testing
Gaps
link.mode ← ""
Check Answer
Spots
1mode = "simplex"
2a_sends = True

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

The 'Parrotfish' badge — Function Builder, one of Cloodit's 106 collectible badges
Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy
Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games
Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print
Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. Which description matches full-duplex transmission?
A. Data travels in both directions at the same time ✓
B. Data travels in one direction only
Full-duplex lets both devices send and receive at once. One direction only is simplex.
2. Which everyday example uses full-duplex transmission?
A. A TV remote control sending a signal to a TV
B. A telephone call ✓
On a phone call both people can talk and hear at the same time. A remote control only sends data one way (simplex).
3. In full-duplex, can a device send and receive data at the same moment?
A. Yes, both at once ✓
B. No, it must take turns
Taking turns describes half-duplex. Full-duplex allows sending and receiving at the same time.
4. A broadband connection lets you download a video while uploading a file. Which type of transmission is this?
A. Full-duplex ✓
B. Simplex
Data moves in both directions at once over broadband, so it is full-duplex.
5. Which statement about full-duplex is TRUE?
A. Only one device can send at a time while the other waits
B. Both devices can send and receive at the same time ✓
Waiting for the other device to finish is half-duplex behaviour, not full-duplex.

Match the Pairs

full-duplex → Data travels in both directions at the same time, so both devices can send and receive at once
Telephone call → Both people can talk and hear each other at the same time, which is an example of full-duplex
Full-duplex lets both devices send and receive at the same moment → Device A <---> Device B (both directions at once)
A broadband connection is full-duplex, so you can upload and download at the same time → Upload + Download = same time
Full-duplex: data goes one way only, like a TV broadcast → This describes simplex transmission. Full-duplex sends data in both directions at the same time.
Full-duplex: devices take turns, so only one can send at a time → This describes half-duplex. In full-duplex both devices can send and receive at the same time.

Key Term

full-duplex
Data is sent in both directions at the same time, so both devices can send and receive at once, for example during a telephone call or over a broadband connection.

Fill in the Blanks

1. link.mode ← "full-duplex" link.example ← "telephone call"
Hint: Type the name of the transmission mode where data goes both ways at once.
2. call.mode ← "full-duplex" call.directions ← 2
Hint: Type the number of directions data can travel at the same time.
3. broadband.canSend ← TRUE broadband.canReceive ← TRUE
Hint: Type the Boolean value showing the device can receive while it is also sending.
4. IF mode = "full-duplex" THEN OUTPUT "send and receive" ENDIF
Hint: Type the pseudocode keyword that starts the code block run when the condition is true.
5. IF canSend AND canReceive THEN OUTPUT "full-duplex" ENDIF
Hint: Type the logical operator meaning both sending and receiving must be possible at once.

Spot the Error

Question 1
A mode = "simplex"
B a_sends = True
C a_receives = True
D print("Both at once")
Line A — Simplex sends data in one direction only. Both devices sending and receiving at the same time is full-duplex, so the line should be mode = "full-duplex".
Question 2
A call = "telephone call"
B mode = "half-duplex"
C print(call, "uses", mode)
Line B — Half-duplex only lets data go both ways one direction at a time. A telephone call lets both people talk and hear at once, so it is full-duplex.
Question 3
A a_sends = True
B a_receives = True
C same_time = False
D print("Full-duplex:", same_time)
Line C — Full-duplex means sending and receiving happen at the same time, so same_time should be True. False would describe half-duplex.
Question 4
A link = "broadband"
B mode = "full-duplex"
C upload = True
D download = False
Line D — A broadband connection is full-duplex, so downloading and uploading both work at the same time. download should be True.
Question 5
A mode = "full-duplex"
B if mode = "full-duplex":
C print("Send and receive")
Line B — A single = assigns a value. To compare mode with "full-duplex" in an if statement you need ==.

Student with a class code? Join your class →