Editing String (computer science) (section)

=== Implementations ===
{{anchor|String Buffers}}
Some languages, such as [[C++]], [[Perl]] and [[Ruby (programming language)|Ruby]], normally allow the contents of a string to be changed after it has been created; these are termed ''mutable'' strings.  In other languages, such as [[Java (programming language)|Java]], [[JavaScript]], [[Lua (programming language)|Lua]], [[Python (programming language)|Python]], and [[Go (programming language)|Go]], the value is fixed and a new string must be created if any alteration is to be made; these are termed ''immutable'' strings. Some of these languages with immutable strings also provide another type that is mutable, such as Java and [[.NET Framework|.NET]]'s {{Javadoc:SE|java/lang|StringBuilder}}, the thread-safe Java {{Javadoc:SE|java/lang|StringBuffer}}, and the [[Cocoa (API)|Cocoa]] <code>NSMutableString</code>. There are both advantages and disadvantages to immutability: although immutable strings may require inefficiently creating many copies, they are simpler and completely [[Thread safety|thread-safe]].

Strings are typically implemented as [[array data type|arrays]] of bytes, characters, or code units, in order to allow fast access to individual units or substrings—including characters when they have a fixed length.  A few languages such as [[Haskell (programming language)|Haskell]] implement them as [[linked list]]s instead.

A lot of high-level languages provide strings as a primitive data type, such as [[JavaScript]] and [[PHP]], while most others provide them as a composite data type, some with special language support in writing literals, for example, [[Java (programming language)|Java]] and [[C Sharp (programming language)|C#]].

Some languages, such as [[C (programming language)|C]], [[Prolog]] and [[Erlang (programming language)|Erlang]], avoid implementing a dedicated string datatype at all, instead adopting the convention of representing strings as lists of character codes. Even in programming languages having a dedicated string type, string can usually be iterated as a sequence character codes, like lists of integers or other values.