Strings

Strings are sequences used to represent text. They are a fundamental data type in many programming languages and in text processing libraries. Depending on the language, a string may be immutable or mutable, and its internal representation may be based on Unicode code points or code units. Most modern systems adopt Unicode, storing strings in encodings such as UTF-8, UTF-16, or UTF-32; UTF-8 is byte-oriented and backward-compatible with ASCII, while UTF-16 and UTF-32 use 2- or 4-byte units for code points. Basic operations include measuring length, indexing and slicing, concatenation, repetition, and searching or replacing substrings. Common utilities also include splitting a string into parts and joining parts into a new string. String literals are written with quotes and often support escape sequences for special characters; many languages provide raw or uninterpreted string forms to avoid escaping.

Unicode adds complexity: a character user sees as one glyph may be composed of multiple code points, and several normalization forms exist (NFC, NFD, NFKC, NFKD) to render text consistently. Normalization and grapheme cluster handling can affect counting and substring operations. I/O and storage require encoding or decoding steps between strings and byte sequences, with attention to encoding errors, endianness, and BOM markers where relevant. Performance considerations include immutability enabling safe sharing, string interning to reduce duplication, and the cost of concatenation in some languages. Strings are used for natural language text, identifiers, message content, and protocol data, making their correct handling essential across systems.