Data gain

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. A student sends the 4-byte message 01001000 01101001 00100001 00101110, but 5 bytes arrive. Which transmission error is this?

A Data gain

B Data loss

2. Which statement correctly describes data gain?

A Extra bits or bytes that were not sent are added to the data

B Some bits or bytes of the data go missing on the way

3. A file is sent as 1000 bytes. The receiver counts 1003 bytes. What has happened?

A Data change: 3 bytes were altered

B Data gain: 3 extra bytes were added

4. Sent: 10110010 01100001. Received: 10110010 01100001 11111111. Which is true?

A An extra byte has been added, so this is data gain

B A byte has been lost, so this is data loss

5. How can you spot data gain by comparing the sent and received messages?

A The received message is shorter than the sent message

B The received message is longer than the sent message

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Sent: 01000001 \| Received: 0100000111		AThe length is the same and one bit has flipped, so this is data change, not data gain.
2Sent: HELLO (5 bytes) \| Received: HELLOX (6 bytes)		BData gain: extra bits that were never sent have been added, so the data arrives longer
3Data gain means the message arrives longer than it was sent		CbytesReceived > bytesSent
4A packet sent with 3 bytes arrives with an extra byte added, giving 4 bytes		Dsent = 3 bytes, received = 4 bytes
5Sent: 5 bytes \| Received: 4 bytes \| Error: data gain		EData gain: one extra byte was added to the message
6Sent: 1011 \| Received: 1111 \| Error: data gain		FFewer bytes arrived than were sent, so this is data loss, not data gain.

Definitions

data gain

Fill in the Blanks

Complete each line of code by filling in the missing parts.

IF receivedLength _ sentLength THEN OUTPUT "Data gain" ENDIF

IF receivedLength > sentLength THEN ______ "Data gain" ENDIF

extraBytes ← receivedLength _ sentLength OUTPUT extraBytes

IF extraBytes > 0 THEN OUTPUT "Data gain" _____

IF ______(received) > LENGTH(sent) THEN OUTPUT "Data gain" ENDIF

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A sent ← 5

B received ← 6

C extra ← received - sent

D IF extra < 0 THEN

E OUTPUT "Data gain"

F ENDIF

Question 2

A sentBytes ← 4

B receivedBytes ← 5

C IF receivedBytes = sentBytes THEN

D OUTPUT "Data gain"

E ENDIF

Question 3

A sent ← "01000001

B received ← "010000011"

C gain ← LENGTH(received) - LENGTH(sent)

D OUTPUT gain

Question 4

A PROCEDURE CheckGain(s, r)

B IF LENGTH(r) > LENGTH(s) THEN

C RETURN TRUE

D ENDIF

E ENDFUNCTION

Question 5

A sLen ← 2

B rLen ← 3

C extra ← sLen - rLen

D OUTPUT extra, " extra bytes"

Answer Key

Data gain

Section A: Quick Questions

A — Data gain

A — Extra bits or bytes that were not sent are added to the data

B — Data gain: 3 extra bytes were added

A — An extra byte has been added, so this is data gain

B — The received message is longer than the sent message

Section B: Match the Pairs

Sent: 01000001 | Received: 0100000111 → Data gain: extra bits that were never sent have been added, so the data arrives longer

Sent: HELLO (5 bytes) | Received: HELLOX (6 bytes) → Data gain: one extra byte was added to the message

Data gain means the message arrives longer than it was sent → bytesReceived > bytesSent

A packet sent with 3 bytes arrives with an extra byte added, giving 4 bytes → sent = 3 bytes, received = 4 bytes

Sent: 5 bytes | Received: 4 bytes | Error: data gain → Fewer bytes arrived than were sent, so this is data loss, not data gain.

Sent: 1011 | Received: 1111 | Error: data gain → The length is the same and one bit has flipped, so this is data change, not data gain.

Section C: Definitions

data gain — Data gain is when extra bits or bytes that were not sent are added to the data, so the message arrives longer than it was sent. It is a type of transmission error.

Section D: Fill in the Blanks

IF receivedLength > sentLength THEN
    OUTPUT "Data gain"
ENDIF

IF receivedLength > sentLength THEN
    OUTPUT "Data gain"
ENDIF

extraBytes ← receivedLength - sentLength
OUTPUT extraBytes

IF extraBytes > 0 THEN
    OUTPUT "Data gain"
ENDIF

IF LENGTH(received) > LENGTH(sent) THEN
    OUTPUT "Data gain"
ENDIF

Section E: Spot the Error

D — Data gain means the message arrives longer than it was sent, so extra must be greater than 0. A negative value would mean data loss. It should be IF extra > 0 THEN.

C — If the two byte counts are equal, the message is the same length and nothing has been gained. Data gain is when more bytes arrive than were sent, so the test should use >.

A — The string is missing its closing quote. It should be sent ← "01000001", the 8 bits that were sent. The received string has 9 bits, so one extra bit has been gained.

A — The block ends with ENDFUNCTION and uses RETURN, so it must start with FUNCTION, not PROCEDURE. It should be FUNCTION CheckGain(s, r).

C — The number of extra bytes is the received length minus the sent length. Subtracting the other way round gives -1. It should be extra ← rLen - sLen.