A Level Computer Science OCR Practice Exam

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How many bits does ASCII use to represent its characters?

5 bits
7 bits
8 bits
16 bits

The correct answer is: 7 bits

ASCII uses 7 bits to represent its characters. This allows for 128 unique characters, which include standard letters, digits, punctuation marks, and control characters. The choice of 7 bits is significant as it can efficiently encode the basic English alphabet and a range of other characters necessary for computing at the time when ASCII was developed. The usage of 7 bits also means that there is an additional bit available in an 8-bit byte, which some implementations use for error checking or to extend the character set to include additional characters in various extended versions of ASCII. However, the fundamental ASCII standard itself defines a set of characters that strictly requires only 7 bits for representation, ensuring compatibility across various systems.