Understanding Variables

Understanding Variables

What is a Variable?

A variable is a named storage location in memory that holds data which can change while the program is running. Variables are one of the most important building blocks in C++.

Declaring Variables

In C++, variables must be declared before they are used. A declaration tells the compiler the variable's type and name. The type indicates what kind of data the variable can hold.

Here are some examples of variable declarations:

int age = 21;     // Stores a whole number
double price = 19.99; // Stores decimal numbers
char grade = 'A'; // Stores a single character
string name = "Tyro"; // Stores text

Common Variable Types

Here are some common variable types in C++:

• int – Stores integers such as 1, 25, or -10.
• float – Stores decimal numbers with less precision.
• double – Stores decimal numbers with higher precision.
• char – Stores a single character like 'A'.
• bool – Stores true or false values.
• string – Stores text or words.

Rules for Naming Variables

When naming variables, you should follow these rules:

• Variable names cannot contain spaces.
• Names cannot start with numbers.
• Use meaningful names like studentAge instead of x.
• C++ is case-sensitive. Age and age are different variables.

Updating Variables

Variables can change during program execution. Here is an example:

int score = 10; // score contains 10
score = 20;    // score now contains 20

Example Program

Here is a simple program that demonstrates declaring and using variables:

#include <iostream>
using namespace std;
int main() {
    string name = "Tyro";
    int age = 21;
    cout << "Name: " << name << endl;
    cout << "Age: " << age << endl;
    return 0;
}

This program declares two variables: name and age. It then prints their values to the console.

Summary

• A variable is a named storage location in memory.
• Variables must be declared before use.
• Common variable types include int, float, double, char, bool, and string.
• Follow naming rules to create meaningful variable names.
• Variables can be updated during program execution.

Check your understanding

1. What is a variable in C++?
2. List three common variable types and their uses.
3. What are the rules for naming variables?
4. Write a simple C++ program that declares two variables and prints their values.