computer programming Computer programming is the process of performing a particular computation (or more generally, accomplishing a specific computing result), usually by designing and building an executable computer program. Programming involves tasks such as anal ...

, a temporary variable is a variable with short lifetime, usually to hold

data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...

that will soon be discarded, or before it can be placed at a more permanent

memory location In computing, a memory address is a reference to a specific memory location used at various levels by software and hardware. Memory addresses are fixed-length sequences of digits conventionally displayed and manipulated as unsigned integers. Su ...

. Because it is short-lived, it is usually declared as a

local variable In computer science, a local variable is a variable that is given ''local scope''. A local variable reference in the function or block in which it is declared overrides the same variable name in the larger scope. In programming languages with o ...

, i.e., a variable with local

scope Scope or scopes may refer to: People with the surname * Jamie Scope (born 1986), English footballer * John T. Scopes (1900–1970), central figure in the Scopes Trial regarding the teaching of evolution Arts, media, and entertainment * CinemaS ...

. There is no formal definition of what makes a variable ''temporary'', but it is an often-used term in programming. A typical example would be that of swapping the contents of two variables. Temporary variables, along with XOR swaps and

arithmetic operators Arithmetic () is an elementary part of mathematics that consists of the study of the properties of the traditional operations on numbers—addition, subtraction, multiplication, division, exponentiation, and extraction of roots. In the 19th ce ...

, are one of three main ways to exchange the contents of two variables. To swap the contents of variables ''a'' and ''b'' one would typically use a temporary variable ''temp'' as follows, so as to preserve the data from ''a'' as it is being overwritten by ''b'': temp := a a := b b := temp Temporary variables are usually named with

identifier An identifier is a name that identifies (that is, labels the identity of) either a unique object or a unique ''class'' of objects, where the "object" or class may be an idea, physical countable object (or class thereof), or physical noncountable ...

s that abbreviate the word ''temporary'', such as ''temp'', ''tmp'' or simply ''t'', or with common

metasyntactic variable A metasyntactic variable is a specific word or set of words identified as a placeholder in computer science and specifically computer programming. These words are commonly found in source code and are intended to be modified or substituted before ...

names, the most common of which are ''foo'', ''bar'', ''baz'' (see also

foobar The terms foobar (), foo, bar, baz, and others are used as metasyntactic variables and placeholder names in computer programming or computer-related documentation. - Etymology of "Foo" They have been used to name entities such as variables, fu ...

). Computer hardware is designed to exploit the behaviour of temporary data: a

cache Cache, caching, or caché may refer to: Places United States * Cache, Idaho, an unincorporated community * Cache, Illinois, an unincorporated community * Cache, Oklahoma, a city in Comanche County * Cache, Utah, Cache County, Utah * Cache Coun ...

register file A register file is an array of processor registers in a central processing unit (CPU). Register banking is the method of using a single name to access multiple different physical registers depending on the operating mode. Modern integrated circuit ...

may contain temporaries internally to a

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

, such that they never need to be committed to

main memory Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a comput ...

(hence consuming no external

memory bandwidth Memory bandwidth is the rate at which data can be read from or stored into a semiconductor memory by a processor. Memory bandwidth is usually expressed in units of bytes/second, though this can vary for systems with natural data sizes that are n ...

See also