computer science

Member variable

Member 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 Member variable rather than just read about it. In short: In object-oriented programming, a member variable (sometimes called a member field) is a variable that is associated with a specific object, and accessible for all its methods (member functions). In class-based programming languages, these are distinguished into two types: class variables (also called static member variables), where only one copy of the variable is shared with all instances of the class; and instanc…

Key takeaways

Member 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 Member variable to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Member variable from memory before moving on to harder problems.

Reference excerpt

In object-oriented programming, a member variable (sometimes called a member field) is a variable that is associated with a specific object, and accessible for all its methods (member functions). In class-based programming languages, these are distinguished into two types: class variables (also called static member variables), where only one copy of the variable is shared with all instances of the class; and instance variables, where each instance of the class has its own independent copy of the variable.

Examples

C++

Java

Python

Common Lisp

Ruby

PHP

Lua

See also Global variable Local variable Property (programming)

References

Worked examples

Example 1 — a first encounter with Member variable

Start with the simplest possible case. Write down what Member 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 Member 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 Member 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 Member variable

In research: Member 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 Member 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: Member variable is common in secondary-school and first-year university syllabi. It links to neighbouring topics Object-oriented programming, Variable (computer science), so understanding it makes those chapters shorter.
In everyday life: Look for Member 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 Member variable in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Member 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 Member variable out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Member variable in simple terms?

Why does Member 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 Member 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 Member variable.