STRING

Strings are sequences of characters used to represent text. In many languages a string is stored as a contiguous sequence of code units. Some languages treat strings as bytes (byte strings), others as sequences of characters or code points. Strings are often immutable, as in Python, Java, and JavaScript, while languages such as C++ or Java provide mutable variants or builders to assemble strings efficiently.

Unicode provides a universal set of characters; however, the bytes that back a string depend on an encoding such as UTF-8, UTF-16, or UTF-32. A string's encoding affects storage, I/O, and interoperability. Modern software often performs normalization to a canonical form (NFC, NFD, NFKC, NFKD) to ensure consistent comparisons and searching.

Common operations include determining length, indexing, slicing, concatenation, searching, replacing, splitting, and joining. Many languages optimize string handling differently: immutable strings may require new allocations on concatenation, while builder types, slices, or views reduce copying.

Special cases include C strings, which are null-terminated byte arrays, introducing potential off-by-one and buffer-overflow risks; many systems wrap them in higher-level types. Performance considerations encourage using dedicated builders or data structures (e.g., ropes) for very large text, and streaming for I/O.

Across locales, grapheme clusters—not just code points—determine what users perceive as a single character. This affects indexing and length when dealing with natural languages and emoji. Strings thus sit at the intersection of encoding, memory, and user perception, and are central to text processing, data serialization, and UI.