ASCII is a character set that gives each character a 7-bit binary code. The codes cover English letters, digits, punctuation and control characters.

The ASCII code for A is 65. What is the code for E?

The ASCII code for E is 69. Letters are coded in alphabetical order, so E sits four places after A.

What is the 7-bit binary pattern for the letter A, whose ASCII code is 65?

The 7-bit ASCII pattern for A is 1000001. The place values 64 + 1 give 65.

How do the ASCII codes for upper-case and lower-case letters differ?

Each lower-case letter's code is 32 more than its upper-case partner. The code for a is 97, while the code for A is 65.

Edexcel GCSE Computer Science 1CP2

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ASCII and the limits of binary representation

3 things to know
Paper 1

Overview

Character sets and 7-bit ASCII, working out codes from A = 65, upper and lower case, the limits of ASCII and Unicode, and the trade-off of using more bits.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is a character set?

Key term

What is ASCII?

Numbers

How many different characters can 7-bit ASCII represent?

Questions from this subtopic

Each one with the model answer underneath.

1
What is a character set?
Model answer
A character set is a list of characters with a unique binary code for each one. The computer stores the code, not the shape of the character.
2
What is ASCII?
Model answer
ASCII is a character set that gives each character a 7-bit binary code. The codes cover English letters, digits, punctuation and control characters.
3
How many different characters can 7-bit ASCII represent?
Model answer
Seven-bit ASCII can represent 128 characters. Seven bits give 2⁷ = 128 codes, numbered 0 to 127.
4
The ASCII code for A is 65. What is the code for E?
Model answer
The ASCII code for E is 69. Letters are coded in alphabetical order, so E sits four places after A.
5
What is the 7-bit binary pattern for the letter A, whose ASCII code is 65?
Model answer
The 7-bit ASCII pattern for A is 1000001. The place values 64 + 1 give 65.
6
How do the ASCII codes for upper-case and lower-case letters differ?
Model answer
Each lower-case letter's code is 32 more than its upper-case partner. The code for a is 97, while the code for A is 65.

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