A binary alphabet with two symbols
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Which statement is true about a binary alphabet?
2. If A = 0 and B = 1, what does the message ABBA mean in 0s and 1s?
3. If X = 0 and O = 1, which message is the same as 1010?
4. Mia writes A = 0 and B = 1. Later she uses A to mean 1. Is this a good key?
5. Key 1: A = 0, B = 1. Key 2: A = 1, B = 0. What does the message AAB mean using Key 2?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1A = 0, B = 1 | A0110 = ABBA = OXXO | |
| 2ABBA | BX = 1, O = 0 | |
| 3Any two different symbols can stand for 0 and 1, such as X and O | CThe same symbol is used for both 0 and 1, so you cannot tell which value it means. Each value needs its own symbol, like A = 0 and B = 1. | |
| 4The same message can be written with different symbols if the key changes | DThe binary message 0110 when A = 0 and B = 1 | |
| 5A = 0, A = 1 | EThe last A was decoded as 0 in one place but the second B was decoded as 0. B always means 1, so ABBA is 0110. | |
| 6Key: A = 0, B = 1. Message: ABBA decoded as 0100 | FA key that says the letter A stands for 0 and the letter B stands for 1 |
C
Definitions
A = 0, B = 1
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
Key: A = 0, B = 1
Message: ABBA
Binary: _110
2.
Key: X = 1, O = 0
Binary: 1001
Message: X_OX
3.
Key: A = 0, B = 1
Binary: 0011
Message: AA_B
4.
Message: ABAB
Key 1: A = 0, B = 1 -> 0101
Key 2: A = 1, B = 0 -> 1_10
5.
Key: X = 0, O = 1
Message: XOOX
Binary: 01_0
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
Key: A = 0, B = 1
B
Key: A = 1, B = 0
C
Binary: 0110
Question 2
A
Key: X = 0, O = 1
B
Message: XXOX
C
Binary: 0100
Question 3
A
Key: Y = 0, Y = 1
B
Message: NNYN
C
Binary: 1101
Question 4
A
Key: A = 0, B = 1
B
Binary: 1001
C
Message: BABA
Question 5
A
Key: # = 0, * = 1
B
Message: **##*
C
Binary: 11010
Answer Key
A binary alphabet with two symbols
Section A: Quick Questions
Q1
B — Any two different symbols can stand for 0 and 1.
Q2
A — 0110
Q3
B — OXOX
Q4
A — No, each symbol must always keep the same meaning.
Q5
A — 110
Section B: Match the Pairs
Q1
A = 0, B = 1 → A key that says the letter A stands for 0 and the letter B stands for 1
Q2
ABBA → The binary message 0110 when A = 0 and B = 1
Q3
Any two different symbols can stand for 0 and 1, such as X and O → X = 1, O = 0
Q4
The same message can be written with different symbols if the key changes → 0110 = ABBA = OXXO
Q5
A = 0, A = 1 → The same symbol is used for both 0 and 1, so you cannot tell which value it means. Each value needs its own symbol, like A = 0 and B = 1.
Q6
Key: A = 0, B = 1. Message: ABBA decoded as 0100 → The last A was decoded as 0 in one place but the second B was decoded as 0. B always means 1, so ABBA is 0110.
Section C: Definitions
Q1
A = 0, B = 1 — A key that lets two different symbols, like A and B, stand for the binary values 0 and 1. Any two symbols work if each one always keeps the same meaning.Section D: Fill in the Blanks
Q1
Key: A = 0, B = 1
Message: ABBA
Binary: 0110Q2
Key: X = 1, O = 0
Binary: 1001
Message: XOOXQ3
Key: A = 0, B = 1
Binary: 0011
Message: AABBQ4
Message: ABAB
Key 1: A = 0, B = 1 -> 0101
Key 2: A = 1, B = 0 -> 1010Q5
Key: X = 0, O = 1
Message: XOOX
Binary: 0110Section E: Spot the Error
Q1
B — The key is swapped, so ABBA would be 1001, not 0110. With A = 0 and B = 1 the message ABBA matches 0110, so the line should be Key: A = 0, B = 1.
Q2
C — X = 0 and O = 1, so XXOX is 0, 0, 1, 0. The binary line should be 0010, not 0100.
Q3
A — A binary alphabet needs two different symbols. Using Y for both 0 and 1 makes it impossible to decode. It should be Key: Y = 0, N = 1.
Q4
C — The binary 1001 is 1, 0, 0, 1, which is B, A, A, B. The message should be BAAB, not BABA.
Q5
B — The binary 11010 uses * for 1 and # for 0, giving **#*#. The broken line has the wrong order, so it should be Message: **#*#.