← ACARA Digital Technologies Years 7–8

What data integrity means in transmission

Data has integrity when it arrives complete (nothing missing or extra) and correct (nothing changed) compared with what was sent.

Part of: ACARA Digital Technologies Years 7–8 — Wired and Wireless Networks — Module 53, QCE Digital Solutions Unit 4 — Digital Methods for Exchanging Data — Module 46, QCE Digital Solutions Unit 4 — Complex Digital Data Exchange Problems and Solution Requirements — Module 81, WA Computer Science ATAR Year 11 — Cyber Security — Module 101

Understanding What data integrity means in transmission in ACARA Digital Technologies Years 7–8

What it does: Each bit in the received data is the same as the bit that was sent, so the data is correct. A protocol adds an extra check value (the parity bit) to the data so the receiver can test whether it arrived intact. Data integrity is about the data matching what was sent, not about speed. Complete means nothing is missing. One lost packet means the data is incomplete. Protocols set rules for checking data, such as parity bits, checksums and acknowledgements. Interference and faults can damage the data while it is transmitted.

Common mistakes: received must be the data that actually arrives over the network, so it should be RECEIVE(). Copying sent into received makes the check always pass, even if the data was damaged. Fewer packets arrived than were sent (4 is less than 5), so the data is incomplete. The message should say 'Data is missing', not that there is extra data.

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This module's key terms are also in a printable crossword (Modules 69–124) and word search (Modules 69–152).

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Learning
Duo
Which statement describes data integrity?
Data travels across the network as fast as possibleData arrives complete and correct, the same as what was sent
Matches
sent: CAT received: CATS -> integrity kept
↓
The extra letter S means data was gained, so the data is not complete and integrity is lost.
Applying
Meanings
Term
data integrity
Meaning
Data has integrity when it arrives complete (nothing missing or extra) and correct (nothing changed) compared with what was sent.
Practice
sent ← "HELLO"
Testing
Gaps
IF received sent THEN integrity ← TRUE
Check Answer
Spots
1sent ← 'HELLO'
2received ← sent

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Quick Questions

1. Which statement describes data integrity?
A. Data travels across the network as fast as possible
B. Data arrives complete and correct, the same as what was sent ✓
Data integrity is about the data matching what was sent, not about speed.
2. A photo is sent as 10 packets but only 9 arrive. What is wrong with its integrity?
A. It is not complete because data is missing ✓
B. It is still complete because most of it arrived
Complete means nothing is missing. One lost packet means the data is incomplete.
3. A message says 'MEET AT 4' but arrives as 'MEET AT 5'. Which part of integrity failed?
A. Correct, because the data was changed ✓
B. Complete, because the message is shorter
The message is the same length, but one character changed. That means the data is not correct.
4. Data arrives with extra bits that the sender never sent. Does it have integrity?
A. Yes, because more data is always better
B. No, because extra data means it is not complete and correct ✓
Integrity means nothing missing and nothing extra. Extra data is a fault too.
5. Which one helps protect data integrity during transmission?
A. A protocol that checks the data and asks for a resend if needed ✓
B. A louder speaker on the sending device
Protocols set rules for checking data, such as parity bits, checksums and acknowledgements.

Match the Pairs

sent: HELLO received: HELLO → The data has integrity: it arrived complete and correct, exactly as it was sent
sent: HELLO received: HELO → Integrity is lost: the data is not complete because a letter went missing
Correct data means nothing was changed in transit, so each character still matches what was sent → sent: 1011 received: 1011
Protocols protect integrity by adding checks, such as a parity bit, that help spot damaged data → data = 1011 + parity bit 1
sent: CAT received: CATS -> integrity kept → The extra letter S means data was gained, so the data is not complete and integrity is lost.
sent: 1100 received: 1000 -> integrity kept → One bit changed from 1 to 0, so the data is not correct and integrity is lost.

Key Term

data integrity
Data has integrity when it arrives complete (nothing missing or extra) and correct (nothing changed) compared with what was sent.

Fill in the Blanks

1. sent ← "HELLO" received ← "HELLO" IF received = sent THEN integrity ← TRUE
Hint: Type the operator that checks the received data is the same as the sent data.
2. sentNum ← 5 gotNum ← 4 IF gotNum < sentNum THEN missing ← TRUE
Hint: Type the operator that shows fewer items arrived than were sent, so the data is not complete.
3. sent ← "1011" received ← "1001" IF received ≠ sent THEN changed ← TRUE
Hint: Type the operator meaning not equal, which shows the data is not correct.
4. sentNum ← 5 gotNum ← 6 IF gotNum > sentNum THEN extra ← TRUE
Hint: Type the operator that shows more items arrived than were sent, so extra data was gained.
5. IF received = sent THEN OUTPUT "Intact" ELSE OUTPUT "Resend needed" ENDIF
Hint: Type the keyword that starts the branch used when the received data does not match, so a protocol can ask for a resend.

Spot the Error

Question 1
A sent ← 'HELLO'
B received ← sent
C IF received = sent THEN
D OUTPUT 'Data is intact'
Line B — received must be the data that actually arrives over the network, so it should be RECEIVE(). Copying sent into received makes the check always pass, even if the data was damaged.
Question 2
A sent ← 5
B got ← 4
C IF got < sent THEN
D OUTPUT 'Data has extra'
Line D — Fewer packets arrived than were sent (4 is less than 5), so the data is incomplete. The message should say 'Data is missing', not that there is extra data.
Question 3
A sent ← 'DOG'
B received ← 'DOT'
C IF received ≠ sent THEN
D OUTPUT 'Data is missing'
Line D — Both words have 3 letters, so nothing is missing. One letter (G) turned into T, so the data was changed. The message should say 'Data was changed'.
Question 4
A complete ← TRUE
B correct ← TRUE
C IF complete OR correct THEN
D OUTPUT 'Integrity kept'
Line C — Data integrity needs the data to be complete AND correct. Using OR would say integrity is kept even when the data is missing pieces or has been changed.
Question 5
A protocol ← 'JPEG'
B SEND data USING protocol
C RESEND packet IF missing
D OUTPUT 'Data arrives intact'
Line A — JPEG is an image file format, not a network protocol. A protocol such as TCP is needed to check packets and ask for missing ones to be resent, which protects integrity.

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