C++ Arithmetic Operators

In this page:

Addition and Subtraction
Multiplication and Division
Modulo Operator
Increment and Decrement Operators
Compound Assignment Operators

Addition and Subtraction

Addition (+) and subtraction (-) work exactly as expected on both integers and floating-point numbers, combining or offsetting two values. These are the building blocks nearly every numeric calculation in a program starts from, whether it's totaling a cart or computing a difference in coordinates.

Example: Addition and Subtraction

cpp

#include <iostream>

int main() {
	int sum = 5 + 3;
	int diff = 5 - 3;
	std::cout << sum << " " << diff << std::endl;
	return 0;
}

Multiplication and Division

Multiplication (*) and division (/) behave differently depending on the operand types: dividing two ints performs integer division, silently discarding any remainder, so 7 / 2 evaluates to 3, not 3.5. To get a fractional result, at least one operand needs to be a floating-point type.

Example: Multiplication and Division

cpp

#include <iostream>

int main() {
	std::cout << 7 / 2 << std::endl;   // integer division: 3
	std::cout << 7.0 / 2 << std::endl; // 3.5
	return 0;
}

Modulo Operator

The modulo operator (%) returns only the remainder left over from integer division and requires both operands to be integers — for example, 10 % 3 evaluates to 1. A very common practical use is checking even/odd with n % 2 == 0, or wrapping a value into a fixed range like cycling through array indices.

Example: Modulo Operator

cpp

#include <iostream>

int main() {
	std::cout << 10 % 3 << std::endl; // remainder: 1
	int n = 8;
	std::cout << (n % 2 == 0) << std::endl; // even check
	return 0;
}

Increment and Decrement Operators

++ and -- adjust a variable by exactly 1, and their position matters: prefix (++x) increments the variable before its new value is used in the surrounding expression, while postfix (x++) uses the original value first and increments afterward. This distinction matters most inside larger expressions like arr[i++], where the timing of the increment changes which element gets accessed.

Example: Increment and Decrement Operators

cpp

#include <iostream>

int main() {
	int x = 5;
	std::cout << ++x << std::endl; // prefix: increments first, prints 6
	std::cout << x++ << std::endl; // postfix: prints 6, then becomes 7
	std::cout << x << std::endl;
	return 0;
}

Compound Assignment Operators

Compound assignment operators like +=, -=, *=, and /= fold an operation and an assignment into one step, so total += price; is shorthand for total = total + price;. Beyond saving keystrokes, this shorthand also reads more clearly as 'update this variable' rather than 'reassign this variable to a new expression involving itself'.

Example: Compound Assignment Operators

cpp

#include <iostream>

int main() {
	int total = 100;
	int price = 20;
	total += price; // shorthand for total = total + price
	std::cout << total << std::endl;
	return 0;
}

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