Which statement correctly compares ASCII, ISO-8859-1 and UTF-8?
LPIC-1 Exam 102-500, objective 107. Administrative tasks medium
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The options
Correct UTF-8 encodes characters in one to four bytes and represents the ASCII characters as the same single bytes ASCII uses
Correct. That backwards compatibility is UTF-8's defining property: any pure-ASCII file is already a valid, identical UTF-8 file, while everything above U+007F uses two to four bytes.
Not correct ISO-8859-1 is a multibyte encoding that can represent any Unicode character
Wrong. ISO-8859-1 (Latin-1) is a single-byte encoding with 256 code points, covering ASCII plus accented characters for Western European languages. It cannot represent Greek, Cyrillic or CJK at all.
Not correct ASCII defines 256 characters, one per byte value
Wrong. ASCII is a 7-bit encoding defining 128 characters, 0 to 127. The various ISO-8859-x sets are what fill the upper 128 values, each differently.
Not correct UTF-8 always uses exactly two bytes per character, which is why it is called a wide encoding
Wrong. UTF-8 is variable width. A fixed-width Unicode encoding does exist — UTF-32 uses four bytes for every character — and UTF-16 uses two or four.
Why
ASCII is 7-bit and defines 128 characters. The ISO-8859 family extends this to 256 single-byte characters, with a different upper half per part (8859-1 Western European, 8859-5 Cyrillic, 8859-15 adds the euro sign). UTF-8 encodes all of Unicode in one to four bytes and keeps ASCII byte-identical, which is why it became the default on Linux. Mixing them is what produces mojibake such as ä where ä was meant.
Where this comes from
- Cited
- LPI exam objective 107.3
- What it says
- Understand the differences between ASCII, ISO-8859 and UTF-8 character encodings.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 107 and space the ones you get wrong.