IGCSE Computer Science Paper 1 Crossword: 2.2 Methods of Error Detection (Modules 168–178)
Name:
Date:
Class:
✎
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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9
Across
- 1. The receiver recalculates the checksum from the received data and compares it with the one sent. Match means no error detected; mismatch means error, so resend is requested. Word 1 of: ___________ and _______ (11)
- 4. A value calculated from a block of data by a set rule and sent with it. The receiver repeats the calculation and compares the results. If they differ, an error occurred. (8)
- 6. Add all the byte values in the block, then keep the remainder after dividing by 256 so the result fits in one byte. Example: 200+100+50=350, 350 mod 256 = 94. Word 2 of: ________ = ___(_____) % 256 (3)
- 9. Multiply each digit by its weight, add them up, divide by 11 and use the remainder (often 11 minus it) as the check digit. A 10 is written X in ISBN-10. Word 1 of: ________ _____ digit (8)
Down
- 2. The receiver sends a copy of the received data back to the sender, who compares it with the original. A match means no error was detected; a mismatch means the data is sent again. Word 2 of: ____ _____ (5)
- 3. An echo check cannot tell if the error happened on the way there or back, and it can miss errors if both trips are damaged the same way. Word 3 of: ____ _____ _____ (5)
- 4. Word 3 of the term in 1 Across: ___________ and _______ (7)
- 5. The last digit of an ______-13, found by weighting the first 12 digits 1 and 3 alternately, adding them, and choosing the digit that makes the total a multiple of 10. Word 1 of: ____-13 _____ digit (4)
- 7. Word 3 of the term in 6 Across: ________ = ___(_____) % 256 (5)
- 8. Word 1 of the term in 2 Down: ____ _____ (4)
Answer Key
IGCSE Computer Science Paper 1 · Modules 168–178
1R
E
2C
A
L
C
U
3L
A
T
E
H
I
4C
H
E
C
K
S
U
M
5I
O
C
I
6S
U
M
K
T
B
P
7B
N
A
8E
Y
R
C
T
9W
E
I
G
H
T
E
D
O
S
Across
1RECALCULATE — The receiver recalculates the checksum from the received data and compares it with the one sent. Match means no error detected; mismatch means error, so resend is requested. Word 1 of: ___________ and _______
4CHECKSUM — A value calculated from a block of data by a set rule and sent with it. The receiver repeats the calculation and compares the results. If they differ, an error occurred.
6SUM — Add all the byte values in the block, then keep the remainder after dividing by 256 so the result fits in one byte. Example: 200+100+50=350, 350 mod 256 = 94. Word 2 of: ________ = ___(_____) % 256
9WEIGHTED — Multiply each digit by its weight, add them up, divide by 11 and use the remainder (often 11 minus it) as the check digit. A 10 is written X in ISBN-10. Word 1 of: ________ _____ digit
Down
2CHECK — The receiver sends a copy of the received data back to the sender, who compares it with the original. A match means no error was detected; a mismatch means the data is sent again. Word 2 of: ____ _____
3LIMIT — An echo check cannot tell if the error happened on the way there or back, and it can miss errors if both trips are damaged the same way. Word 3 of: ____ _____ _____
4COMPARE — Word 3 of the term in 1 Across: ___________ and _______
5ISBN — The last digit of an ______-13, found by weighting the first 12 digits 1 and 3 alternately, adding them, and choosing the digit that makes the total a multiple of 10. Word 1 of: ____-13 _____ digit
7BYTES — Word 3 of the term in 6 Across: ________ = ___(_____) % 256
8ECHO — Word 1 of the term in 2 Down: ____ _____