From MoodleDocs

The American Standard Code for Information Interchange (ASCII) is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text. It was a standard for many years.

ASCII has the potential for 128 characters, 33 non printing and 94 printing. This was a fixed 7 byte system. It was difficult to use with written language systems that use 100s or 1000s of characters.

Moodle uses UTF-8, which is backward compatible with ASCII.

See also