← IGCSE Computer Science Paper 1

Parallel transmission

Sends several bits at the same time, each down its own wire in the same cable, e.g. 8 bits down 8 wires at once.

Part of: IGCSE Computer Science 0478 — 2.1 Data Transmission Types and Methods — Module 24, WA Computer Science ATAR Year 11 — Network Communications — Module 17

Understanding Parallel transmission in IGCSE Computer Science Paper 1

What it does: The number of bits sent at once matches the number of wires, because each bit has its own wire. The wires used for parallel transmission are bundled together in one cable.

Common mistakes: Eight wires carrying 8 bits at once is parallel transmission, not serial. Serial sends bits one after another down a single wire. The line should be TYPE: parallel. In parallel transmission each bit travels down its own wire. Bits sharing one wire describes serial transmission. The line should be: Each bit has its own wire.

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This module's key terms are also in a printable crossword (Modules 121–130) and word search (Modules 121–141).

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Learning
Duo
Which describes parallel transmission?
Several bits are sent at the same time, each down its own wireBits are sent one after another down a single wire
Matches
Parallel transmission: 8 bits sent one after another down 1 wire
↓
This describes serial transmission, not parallel. Parallel sends the bits at the same time, each on its own wire.
Applying
Meanings
Term
parallel transmission
Meaning
Sends several bits at the same time, each down its own wire in the same cable, e.g. 8 bits down 8 wires at once.
Practice
byte ← "10110010"
Testing
Gaps
wires ←
Check Answer
Spots
1TYPE: serial
2WIRES: 8

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Quick Questions

1. Which describes parallel transmission?
A. Bits are sent one after another down a single wire
B. Several bits are sent at the same time, each down its own wire ✓
Parallel transmission uses many wires so several bits travel at once. Sending bits one after another is serial transmission.
2. How many wires could send 8 bits at the same time in parallel transmission?
A. 1 wire shared by all 8 bits
B. 8 wires, one for each bit ✓
Each bit gets its own wire, so 8 bits at once needs 8 wires.
3. Where are the wires in parallel transmission found?
A. Several wires together in the same cable ✓
B. Each wire is in a separate cable
The wires used for parallel transmission are bundled together in one cable.
4. True or false: in parallel transmission, 8 bits are sent down 8 wires at once.
A. True ✓
B. False
This is the classic example. One byte (8 bits) is sent in one go, with one bit on each wire.
5. A cable has 8 wires and each wire carries one bit at the same moment. Which type of transmission is this?
A. Parallel transmission ✓
B. Serial transmission
Several bits sent at the same time down separate wires is parallel transmission.

Match the Pairs

parallel transmission → Sends several bits at the same time, each down its own wire in the same cable
8 bits, 8 wires → A byte is sent all at once, with every bit using its own wire
Parallel transmission sends several bits at the same time, each down its own wire → wires = 8; bits_at_once = 8
A parallel cable contains several wires side by side in one cable → cable = [wire1, wire2, wire3, wire4, wire5, wire6, wire7, wire8]
Parallel transmission: 8 bits sent one after another down 1 wire → This describes serial transmission, not parallel. Parallel sends the bits at the same time, each on its own wire.
Parallel transmission: 8 bits sent at once down 1 wire → Each bit needs its own wire. One wire cannot send 8 bits at the same time.

Key Term

parallel transmission
Sends several bits at the same time, each down its own wire in the same cable, e.g. 8 bits down 8 wires at once.

Fill in the Blanks

1. bits ← 8 wires ← bits
Hint: Type the variable name so the cable has one wire for every bit.
2. method ← "parallel"
Hint: Type the name of the method that sends several bits at once, each down its own wire.
3. IF bitsAtOnce > 1 THEN method ← "parallel" ENDIF
Hint: Type the comparison operator that checks for more than one bit sent at the same time.
4. serialWires ← 1 parallelWires ← serialWires * 8
Hint: Type the arithmetic operator that scales one wire up to eight wires.
5. cable ← ["w1","w2","w3","w4"] wires ← LENGTH(cable)
Hint: Type the function that counts how many wires are in the one cable.

Spot the Error

Question 1
A TYPE: serial
B WIRES: 8
C BITS AT ONCE: 8
Line A — Eight wires carrying 8 bits at once is parallel transmission, not serial. Serial sends bits one after another down a single wire. The line should be TYPE: parallel.
Question 2
A Parallel transmission:
B All bits share one wire
C All wires are in one cable
Line B — In parallel transmission each bit travels down its own wire. Bits sharing one wire describes serial transmission. The line should be: Each bit has its own wire.
Question 3
A wires ← 8
B bits ← 8
C ticks ← bits * wires
D OUTPUT ticks
Line C — With 8 wires, 8 bits are sent in 1 tick, because all the bits travel at the same time. The number of ticks is bits / wires, not bits * wires.
Question 4
A FOR w ← 1 TO 8
B SEND 8 bits down wire[w]
C NEXT w
Line B — Each wire carries only one bit at a time. The 8 bits are spread across 8 wires, so each wire gets 1 bit, not 8.
Question 5
A wires ← 16
B bitsAtOnce ← 1
C OUTPUT bitsAtOnce
Line B — Each wire carries one bit, so 16 wires send 16 bits at once. bitsAtOnce should be set to wires, not 1.

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