IGCSE Computer Science Paper 1 Crossword: 2.2 Methods of Error Detection (Modules 179–188)
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Crossword
Read each clue and write the matching term in the grid. Numbers in brackets show the letters in each word.
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Across
- 4. A wrong number can still pass the check digit test, and a valid number may belong to the wrong item. The check digit tests the digits only, not what they mean. Word 3 of: check _____ __________ (10)
- 7. Parity, parity block, checksum and echo check find errors in transmission; a check digit finds them at data entry; ARQ asks for a resend. Each sends different extra data. Word 2 of: error _________ ______ (9)
- 8. The last ______ of a bar code number, worked out from the other digits. The scanner recalculates it and rejects a misread if the digits do not match, so the item must be scanned again. Word 2 of: check _____ (5)
- 9. Word 1 of the term in 6 Down: ___________ and _______ (11)
- 10. Word 3 of the term in 7 Across: error _________ ______ (6)
Down
- 1. A message (NAK) the receiver sends to the sender when the error check fails, telling it the data arrived with an error so the sender must resend the same data. Word 1 of: ________ acknowledgement (8)
- 2. ARQ resends data when a separate check finds an error, so it misses errors that check misses, and a noisy link causes many resends that slow the transfer. Word 2 of: ARQ ______ (6)
- 3. A message sent by the receiver to tell the sender that data arrived without error. Often written ACK. It is sent only after the error check passes, so the sender can send the next data. Word 1 of: ________ acknowledgement (8)
- 5. The set time a sender waits for an acknowledgement after sending data. If none arrives in time, it assumes the data was lost and resends it. (7)
- 6. Work out the check digit again from the other digits, then ______ it with the one entered. If they differ, reject the number and ask the user to re-enter it. Word 3 of: ___________ and _______ (7)
Answer Key
IGCSE Computer Science Paper 1 · Modules 179–188
1N
E
G
2L
A
3P
4L
I
M
I
5T
A
T
I
O
N
M
I
I
S
I
M
V
I
6C
T
7D
E
T
E
C
T
I
O
N
S
O
I
M
U
V
P
8D
I
G
I
T
9R
E
C
A
L
C
U
L
A
T
E
R
10M
E
T
H
O
D
Across
4LIMITATION — A wrong number can still pass the check digit test, and a valid number may belong to the wrong item. The check digit tests the digits only, not what they mean. Word 3 of: check _____ __________
7DETECTION — Parity, parity block, checksum and echo check find errors in transmission; a check digit finds them at data entry; ARQ asks for a resend. Each sends different extra data. Word 2 of: error _________ ______
8DIGIT — The last ______ of a bar code number, worked out from the other digits. The scanner recalculates it and rejects a misread if the digits do not match, so the item must be scanned again. Word 2 of: check _____
9RECALCULATE — Word 1 of the term in 6 Down: ___________ and _______
10METHOD — Word 3 of the term in 7 Across: error _________ ______
Down
1NEGATIVE — A message (NAK) the receiver sends to the sender when the error check fails, telling it the data arrived with an error so the sender must resend the same data. Word 1 of: ________ acknowledgement
2LIMITS — ARQ resends data when a separate check finds an error, so it misses errors that check misses, and a noisy link causes many resends that slow the transfer. Word 2 of: ARQ ______
3POSITIVE — A message sent by the receiver to tell the sender that data arrived without error. Often written ACK. It is sent only after the error check passes, so the sender can send the next data. Word 1 of: ________ acknowledgement
5TIMEOUT — The set time a sender waits for an acknowledgement after sending data. If none arrives in time, it assumes the data was lost and resends it.
6COMPARE — Work out the check digit again from the other digits, then ______ it with the one entered. If they differ, reject the number and ask the user to re-enter it. Word 3 of: ___________ and _______