computer programming Computer programming or coding is the composition of sequences of instructions, called computer program, programs, that computers can follow to perform tasks. It involves designing and implementing algorithms, step-by-step specifications of proc ...

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

data Data ( , ) are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted for ...

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

, i.e., a variable with local scope. 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, 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, person, physical countable object (or class thereof), or physical mass ...

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, qux, quux, 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 v ...

Computer hardware Computer hardware includes the physical parts of a computer, such as the central processing unit (CPU), random-access memory (RAM), motherboard, computer data storage, graphics card, sound card, and computer case. It includes external devices ...

is designed to exploit the behaviour of temporary data: a cache or

register file A register file is an array of processor registers in a central processing unit (CPU). The instruction set architecture of a CPU will almost always define a set of registers which are used to stage data between memory and the functional units on ...

may contain temporaries internally to a

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

, such that they never need to be committed to

main memory Computer data storage or digital 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 processin ...

(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 ...

See also