Codepages

Codepages, also called code pages or character maps, are mappings between 8-bit byte values and characters used by a computing system to display text. Each code page defines up to 256 characters, though some values may be reserved for control codes rather than printable characters. Code pages are often identified by a number, especially in IBM and Microsoft ecosystems (for example code page 437).

Historically, there was no universal standard for representing characters beyond the basic ASCII set. The IBM PC introduced code page 437, which provided printable characters for English and some additional symbols. Over time, other code pages added support for more languages, leading to a proliferation of encodings. ISO/IEC 8859 standards offered several 8-bit encodings for different language groups, such as ISO-8859-1 (Latin-1). Windows developed its own family of code pages (for instance Windows-1252, Windows-1251). Some encodings, like Shift JIS and GB2312, use multiple bytes per character, so they are not strictly single-byte code pages, but they are still commonly referred to as code pages.

Common examples include ASCII (0–127), ISO-8859-1 (Latin-1) for Western European languages, Windows-1252, Windows-1251 for Cyrillic, Shift JIS for Japanese, GB2312 and its successors for Chinese, and EUC-KR for Korean. MacRoman is another historical example.

Issues with codepages arise when text encoded in one code page is misinterpreted as another, producing mojibake. With the widespread adoption of Unicode and UTF-8, new data often avoids code pages, but legacy data, software, and systems continue to rely on them. Modern software typically supports conversion between code pages and Unicode to maintain compatibility.