Codesnonprintable

Codesnonprintable is a term used to describe character codes that are not intended to render visible glyphs in typical text displays. It includes ASCII control characters (the C0 range U+0000 to U+001F and the delete code U+007F) and, in environments that implement ISO/IEC 6429, the C1 control set (U+0080 to U+009F). In Unicode, many formatting and control characters are classified as nonprinting and may influence layout, direction, or typography without producing a visible symbol.

Common examples of codesnonprintable include NUL (U+0000), BEL (U+0007), CR (U+000D), and LF (U+000A); the soft hyphen (U+00AD); zero width spaces (U+200B), zero width non-joiner (U+200C), and zero width joiner (U+200D); the word joiner (U+2060); and a range of directional and formatting characters such as LRE (U+202A), RLE (U+202B), PDF (U+202C), LRO (U+202D), RLO (U+202E), as well as LRM (U+200E) and RLM (U+200F). The byte-order mark or BOM (U+FEFF) is another example encountered at file boundaries. These characters are generally invisible on screen but can affect rendering, data processing, or transmission.

Applications of codesnonprintable span text processing, terminal control, and data sanitization. They are essential for formatting, bidirectional text handling, and encoding signals, but they can cause issues in logs, searches, or input validation if not properly handled. Security and reliability considerations include preventing obfuscated input or injection via nonvisible characters and ensuring robust filtering or escaping when necessary.

Handling typically involves detecting and either removing, escaping, or preserving only the intended subset of nonprintable characters, depending on the context and requirements.