C++ Fundamentals · Variables & Data Types · Lesson 4 of 24

Declaring Variables

Concept

Declaring Variables

C++ variables must declare a type up front, such as int, double, char, or bool, before you can use them.

By the end of this lesson

Explain the core idea behind Declaring Variables.
Predict output before running a change.
Test one realistic and one unusual input.
Use the result to make the next decision.

How to study this page

1. Read one concept.
2. Change the example.
3. Run, compare, and explain.
4. Complete the challenge below.

ExampleRunnable

int age = 20;
double price = 9.99;
char grade = 'A';
bool isStudent = true;

Try it Yourself »

Self-check before continuing

Without looking at the example, describe what changes when you modify one input in Declaring Variables. Then reopen the editor and prove your explanation with a small test.

You are ready to continue when you can predict, test, and explain the result.

Your turn

Declare one variable of each type shown above with your own values.

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Console

Output will appear here...