leegteken

Leegteken, in computing commonly referred to as the null character or NUL, is a control character with the Unicode code point U+0000. It has no visible glyph and is not intended to produce a printed symbol. In ASCII it is defined by the value 0x00; in UTF-8 it is encoded as a single zero byte.

Purpose and usage: In many programming languages derived from C, the NUL serves as a terminator for strings; strings are stored as a sequence of bytes ending with NUL. This convention makes it a sentinel rather than a visible element in text. Beyond strings, the NUL can be used as a data delimiter or placeholder in binary protocols, file formats, or memory structures. It is typically not treated as a printable character in ordinary text.

Representation and handling: Because it is non-printable, it usually does not display; editors may render it as a blank space, a box, or a label such as "NUL." Some languages and libraries permit including NUL within strings (for example, in Python or Java), but others treat it as an end-of-string marker (most notably C and C++), which affects how strings are processed and transmitted.

Security and compatibility: Null-byte injection can be a concern in systems that separate string data from their terminators, potentially leading to truncation, parsing errors, or vulnerabilities when interacting with C APIs, databases, or file systems. Handling of the NUL character varies across languages, runtimes, and data formats, making awareness of its presence important in software development and data processing.

See also: Null character, ASCII NUL, Unicode.