Oxford, Cambridge and RSA (OCR) GCSE Computer Science Practice Exam

The character set that consists of 128 characters and is 7-bit encoded is ASCII (American Standard Code for Information Interchange). ASCII was developed in the early years of computer communication and provides a standard way to represent text in computers.

In ASCII, each character is represented by a 7-bit binary number, allowing for a total of 128 different characters, which includes control characters (like newline or carriage return), digits (0-9), uppercase letters (A-Z), lowercase letters (a-z), and some special characters (like punctuation marks). This standard is foundational in computer science as it allows for text to be consistently represented across different systems.

The other character sets mentioned do not fit the criteria of being 7-bit and having exactly 128 characters. UTF-8 is a variable-length encoding system that can represent all Unicode characters and uses one to four bytes. ISO-8859-1 is an 8-bit character set that extends ASCII to include additional characters commonly used in Western European languages. ANSI is often used interchangeably with ISO-8859-1 but can refer to a variety of character encodings as well and also uses 8 bits. Therefore, ASCII is the correct choice in this context.