Nullterminated

Nullterminated refers to a string representation in which the sequence of characters is followed by a terminating null character. In practice, this means a contiguous block of memory stores characters and ends with a byte valued zero (the NUL or '\0'). This convention is most closely associated with the C and C++ languages, where strings are typically represented as arrays or pointers to char.

In null-terminated strings, the length is not stored separately. Instead, functions such as strlen, strcpy, and strcat determine the end of the string by scanning for the first zero byte. Because the terminator marks the end, embedded null bytes inside the data cannot occur; any 0 byte within the string would prematurely signal termination.

Advantages of this approach include a simple memory layout without an explicit length field and broad compatibility with existing C-based APIs. It also minimizes per-string metadata, which can be advantageous in low-level programming.

Disadvantages include potential safety and performance issues. Manually maintaining a correct terminator is error-prone; missing or extra terminators can lead to buffer overreads, crashes, or security vulnerabilities. Calculating the length of a string requires a linear scan, which can be inefficient for long strings. Additionally, null-terminated strings are not suitable for arbitrary binary data that may legitimately contain zero bytes.

Variants and alternatives include length-prefixed strings, which store the size alongside the data, or using language-provided string types that manage memory and termination automatically. The term “C-style string” is often used to describe null-terminated strings and the APIs that operate on them.