Type casting in C++

Introduction

Type casting helps you change a value from one type to another. It is useful when you want to treat data differently or avoid errors.

When you want to convert a floating-point number to an integer to remove decimals.

When you need to treat a number as a different type to perform specific operations.

When you want to convert between compatible pointer types.

When you want to force a conversion that the compiler does not do automatically.

When you want to make your intentions clear to other programmers reading your code.

Syntax

C++

type new_variable = (type) old_variable;  // C-style cast
new_variable = static_cast<type>(old_variable);  // C++ style cast

C++ prefers static_cast because it is safer and clearer.

C-style casts can do many conversions but are less safe and harder to find in code.

Examples

This converts integer a to double using C-style cast.

C++

int a = 10;
double b = (double) a;

This converts double x to int using static_cast, dropping decimals.

C++

double x = 9.7;
int y = static_cast<int>(x);

This converts character c to its ASCII integer value.

C++

char c = 'A';
int ascii = static_cast<int>(c);

Sample Program

This program shows how to convert a double to an int and a char to its ASCII integer value using static_cast.

C++

#include <iostream>

int main() {
    double pi = 3.14159;
    int intPi = static_cast<int>(pi);  // convert double to int

    std::cout << "Original double: " << pi << "\n";
    std::cout << "After casting to int: " << intPi << "\n";

    char letter = 'Z';
    int asciiValue = static_cast<int>(letter);  // char to int
    std::cout << "Character: " << letter << " has ASCII value: " << asciiValue << "\n";

    return 0;
}

Important Notes

When casting from floating-point to integer, the decimal part is dropped, not rounded.

Use static_cast for most conversions to keep code clear and safe.

Be careful when casting pointers; improper casts can cause crashes.

Summary

Type casting changes a value from one type to another.

Use static_cast in C++ for safe and clear conversions.

Casting helps avoid errors and makes your code intentions clear.