Characters: ASCII and Unicode

Computers store everything as binary numbers, so text characters (letters, digits, symbols) must also be represented using binary codes. This lesson covers the two main character encoding systems: ASCII and Unicode.

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What Is a Character Set?

A character set is a defined list of characters that a computer can recognise and store. Each character in the set is assigned a unique binary code (a number). The character set determines which characters are available and how many bits are needed to store each one.

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ASCII (American Standard Code for Information Interchange)

ASCII was one of the earliest character encoding standards, developed in the 1960s. It was designed primarily for the English language.

Key Facts about ASCII

• Uses 7 bits per character (standard ASCII), giving 128 possible characters (0–127).
• Extended ASCII uses 8 bits (1 byte), giving 256 possible characters (0–255).
• Includes uppercase letters (A–Z), lowercase letters (a–z), digits (0–9), punctuation marks, and control characters (such as newline, tab, and backspace).
• Each character has a unique numerical code called its ASCII value or code point.

Selected ASCII Values