Even parity
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. A system uses even parity. The 7 data bits are 1011000. What should the parity bit be?
2. A system uses even parity. The 7 data bits are 0110011. What should the parity bit be?
3. A system uses even parity. The 7 data bits are 0000000. What should the parity bit be?
4. Which statement describes even parity?
5. With even parity, the data bits contain an odd number of 1s. What is the parity bit?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 11011001 + parity bit 0 -> 10110010 | AThe data 1100110 already has four 1s (even), so the parity bit should be 0. Adding 1 makes five 1s, which is odd. | |
| 20110100 + parity bit 1 -> 01101001 | BThe data 1011001 has four 1s, which is already even, so the even parity bit is 0 | |
| 3Data with no 1s at all still has an even count of 1s, because 0 is even, so the even parity bit is 0 | CThe data 1000001 has two 1s, which is even, so parity bit 0 is right. The error is in a different case: the learner counted 0s instead of 1s. | |
| 4With even parity, an odd number of 1s in the data means the parity bit is set to 1 to make the total even | D1110000 + parity bit 1 -> 11100001 | |
| 51100110 + parity bit 1 -> 11001101 | EThe data 0110100 has three 1s, which is odd, so the even parity bit is 1 to make the total four | |
| 61000001 + parity bit 0 -> 10000010 | F0000000 + parity bit 0 -> 00000000 |
C
Definitions
even parity
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
data = 1011001
ones = 4 (even)
parity bit = _
2.
data = 0110100
ones = 3 (odd)
parity bit = _
3.
data = 0000000
ones = 0, which is an even count
parity bit = _
4.
Even parity makes the number of 1s ____
5.
data = 1101110
ones = _
parity bit = 1
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
data = "1011001"
B
ones = data.count("0")
C
if ones % 2 == 0:
D
parity = 0
E
else:
F
parity = 1
Question 2
A
bits = 1100110
B
ones = bits.count("1")
C
parity = ones % 2
D
print(bits + str(parity))
Question 3
A
ones ← 4
B
IF ones MOD 2 = 0 THEN
C
parity ← 1
D
ELSE
E
parity ← 1
F
ENDIF
Question 4
A
def even_parity(bits):
B
ones = bits.count("1")
C
return ones // 2
D
print(even_parity("1011000"))
Question 5
A
data = "0000000"
B
ones = data.count("1")
C
parity = 1
D
print(parity)
Answer Key
Even parity
Section A: Quick Questions
Q1
B — 1
Q2
A — 0
Q3
A — 0, because zero 1s is an even count
Q4
A — The total number of 1s, including the parity bit, is even
Q5
B — 1
Section B: Match the Pairs
Q1
1011001 + parity bit 0 -> 10110010 → The data 1011001 has four 1s, which is already even, so the even parity bit is 0
Q2
0110100 + parity bit 1 -> 01101001 → The data 0110100 has three 1s, which is odd, so the even parity bit is 1 to make the total four
Q3
Data with no 1s at all still has an even count of 1s, because 0 is even, so the even parity bit is 0 → 0000000 + parity bit 0 -> 00000000
Q4
With even parity, an odd number of 1s in the data means the parity bit is set to 1 to make the total even → 1110000 + parity bit 1 -> 11100001
Q5
1100110 + parity bit 1 -> 11001101 → The data 1100110 already has four 1s (even), so the parity bit should be 0. Adding 1 makes five 1s, which is odd.
Q6
1000001 + parity bit 0 -> 10000010 → The data 1000001 has two 1s, which is even, so parity bit 0 is right. The error is in a different case: the learner counted 0s instead of 1s.
Section C: Definitions
Q1
even parity — A parity bit is added so the total number of 1s in the byte, including the parity bit, is even. Odd count of 1s in the data gives parity bit 1; even count (even 0) gives 0.Section D: Fill in the Blanks
Q1
data = 1011001
ones = 4 (even)
parity bit = 0Q2
data = 0110100
ones = 3 (odd)
parity bit = 1Q3
data = 0000000
ones = 0, which is an even count
parity bit = 0Q4
Even parity makes the number of 1s evenQ5
data = 1101110
ones = 5
parity bit = 1Section E: Spot the Error
Q1
B — Parity depends on the number of 1s in the data, so the code must count "1", not "0". The line should be ones = data.count("1").
Q2
A — The bits must be stored as a string in quotes so that .count("1") works on them. Without quotes it is a number and the program fails. It should be bits = "1100110".
Q3
C — Four 1s is an even count, and the data already has an even number of 1s. With even parity the parity bit must therefore be 0, not 1. The line should be parity ← 0.
Q4
C — The parity bit is the remainder after dividing the number of 1s by 2, which is 0 for an even count and 1 for an odd count. // gives the whole-number quotient instead. It should be return ones % 2.
Q5
C — Zero 1s is an even count, because 0 is even. The data already has an even number of 1s, so the even parity bit is 0. The line should be parity = ones % 2, which gives 0.