Character encoding
Mapping characters to binary representations enabling text storage and transmission. ASCII encodes 128 characters using 7 bits. Unicode extends encoding to represent characters from all languages. Different encodings (UTF-8, UTF-16) optimize space or compatibility.
Real World
Emoji like 😀 only work because Unicode assigns code point U+1F600, and UTF-8 encodes it in 4 bytes — before Unicode, Japanese users on Shift-JIS systems saw garbled text when emailing European users on ISO-8859-1.
Exam Focus
Compare ASCII (7-bit, 128 characters) with Unicode (variable-length, 100k+ characters) — always state that UTF-8 is backwards-compatible with ASCII.
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