← IGCSE Computer Science Paper 1

Parity byte

An extra byte sent after a block of data bytes. Each of its bits is the parity bit for one column (bit position) taken down across all the data bytes in the block.

Part of: IGCSE Computer Science 0478 — 2.2 Methods of Error Detection — Module 17

Understanding Parity byte in IGCSE Computer Science Paper 1

What it does: The first three bytes are the data block. The last byte, 00010100, is the single parity byte for all three. Column 6 has one 1, which is odd. Even parity needs a 1 to make the total even, so this parity byte bit is 1.

Common mistakes: Column 6 holds 0 and 1, which is one 1. Even parity needs the parity bit to be 1 so the column total is even. The parity byte should be 11011110. A parity byte is not made for each data byte. One parity byte is made for the whole block of data bytes.

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 Parity byte to a class →

This module's key terms are also in a printable crossword (Modules 155–164) and word search (Modules 142–164).

Take this worksheet further — free with Cloodit

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

Learning

Duo

Where is the parity byte sent in a block of data?

After the data bytes of the blockBefore the first data byte

Matches

00010100 10110010 01100001 11000111

↓

The parity byte is sent before the data bytes. It must be sent after them, as the last byte of the block.

Applying

Meanings

Term

parity byte

Meaning

An extra byte sent after a block of data bytes. Each of its bits is the parity bit for one column (bit position) taken down across all the data bytes in the block.

Practice

Data 1: 10110010

Testing

Gaps

SEND byte

Check Answer

Spots

2Byte 2: 01101100

3Parity: 11011010

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

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. Where is the parity byte sent in a block of data?

A. After the data bytes of the block ✓

B. Before the first data byte

The parity byte is an extra byte added at the end, after all the data bytes in the block.

2. What does each bit of the parity byte act as the parity bit for?

A. One column (bit position) down all the bytes ✓

B. One row (a single data byte)

Each bit of the parity byte checks a column, which is the same bit position taken from every data byte.

3. A block has 6 data bytes. How many parity bytes does the block use?

A. One parity byte for each data byte

B. One parity byte for the whole block ✓

A block has a single parity byte sent after all of its data bytes. Each data byte keeps its own parity bit separately if one is used.

4. Which statement describes column parity?

A. Bit 0 of the parity byte checks all 8 bits of the first data byte

B. Bit 0 of the parity byte checks bit 0 of every data byte ✓

Column parity works down the columns, so bit 0 of the parity byte covers bit 0 of every data byte in the block.

5. The data bytes are 8 bits long. How many bits does the parity byte have?

A. 8 bits, one for each column ✓

B. 1 bit, for the whole block

There are 8 columns (bit positions), so the parity byte needs 8 bits, one parity bit for each column.

Match the Pairs

Column 1 down: 1,0,1 -> parity bit 0 → Bit 1 of the parity byte comes from the first bit of every data byte. Two 1s is even, so with even parity this bit is 0.

BYTE1 BYTE2 BYTE3 PARITYBYTE → The parity byte is sent after all the data bytes in the block, as the last byte.

One parity byte is sent for the whole block of data bytes, as the last byte (even parity). → 10110010 01100001 11000111 00010100

Each bit of the parity byte is worked out by counting the 1s down one column of the block. → Column 6 down: 0,0,1 -> parity bit 1

00010100 10110010 01100001 11000111 → The parity byte is sent before the data bytes. It must be sent after them, as the last byte of the block.

Parity byte bit 1 = parity of 10110010 → This uses one data byte (a row) instead of a column. Bit 1 of the parity byte must come from the first bit of every data byte.

Key Term

parity byte

An extra byte sent after a block of data bytes. Each of its bits is the parity bit for one column (bit position) taken down across all the data bytes in the block.

Fill in the Blanks

1. SEND data bytes SEND parity byte

Hint: Type the word that names the extra byte sent after the data bytes.

2. Column 1 bits: 1, 0, 1, 1 Even parity bit for column 1 = 1

Hint: Count the 1s down the column, then choose the bit that makes the total even.

3. Each parity byte bit checks one column

Hint: Type the word for the bit position taken down across all the data bytes.

4. data bytes in block = 4 parity bytes needed = 1

Hint: Type how many parity bytes are sent for the whole block of data bytes.

5. Column 3 bits: 0, 0, 1, 0 Odd parity bit for column 3 = 0

Hint: Count the 1s down the column and decide whether a 1 is needed to make the total odd.

Spot the Error

Question 1

A Byte 1: 10110010

B Byte 2: 01101100

C Parity: 11011010

Line C — Column 6 holds 0 and 1, which is one 1. Even parity needs the parity bit to be 1 so the column total is even. The parity byte should be 11011110.

Question 2

A Parity byte: one per byte

B Each bit covers one column

C Sent after the data bytes

Line A — A parity byte is not made for each data byte. One parity byte is made for the whole block of data bytes.

Question 3

A Byte 1: 11000011

B Byte 2: 10100000

C Odd parity byte: 01100011

Line C — 01100011 is the even parity byte. With odd parity each column, including the parity bit, must hold an odd number of 1s. The correct parity byte is 10011100.

Question 4

A Byte 1: 10000001

B Byte 2: 00110000

C Byte 3: 01010101

D Parity: 11100110

Line D — Column 7 is 0, 0, 0 with no 1s, so even parity needs a parity bit of 0. The parity byte should be 11100100.

Question 5

A FOR each column (even parity)

B COUNT the 1s along each byte

C IF the count is odd

D PRINT error found

Line B — A parity byte is checked column by column. The 1s must be counted down each column across all the bytes, not along each byte.

Student with a class code? Join your class →