A symbol in computer programming is a primitive data type whose instances have a unique human-readable form. Symbols can be used as identifiers. In some programming languages, they are called atoms. Uniqueness is enforced by holding them in a symbol table. The most common use of symbols by programmers is for performing language reflection (particularly for callbacks), and most common indirectly is their use to create object linkages. In the most trivial implementation, they are essentially named integers (e.g. the enumerated type in C).