computer science

Temporary variable

Temporary variable is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Temporary variable rather than just read about it. In short: In computer programming, a temporary variable is a variable with short lifetime, usually to hold data 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, i.e., a variable with local scope.

Key takeaways

Temporary variable belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Temporary variable to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Temporary variable from memory before moving on to harder problems.

Reference excerpt

In computer programming, a temporary variable is a variable with short lifetime, usually to hold data 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, 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 := b b := temp

Temporary variables are usually named with identifiers that abbreviate the word temporary, such as temp, tmp or simply t, or with common metasyntactic variable names, the most common of which are foo, bar, baz (see also foobar). Computer hardware is designed to exploit the behaviour of temporary data: a cache or register file may contain temporaries internally to a microprocessor, such that they never need to be committed to main memory (hence consuming no external memory bandwidth).

Worked examples

Example 1 — a first encounter with Temporary variable

Start with the simplest possible case. Write down what Temporary variable claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Temporary variable before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Temporary variable ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Temporary variable

In research: Temporary variable appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Temporary variable in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Temporary variable is common in secondary-school and first-year university syllabi. It links to neighbouring topics Variable (computer science), so understanding it makes those chapters shorter.
In everyday life: Look for Temporary variable outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Temporary variable in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Temporary variable means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Temporary variable out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Temporary variable in simple terms?

Why does Temporary variable matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Temporary variable?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Temporary variable.