C++ Relational Operators

Relational operators compare two values, like asking who is taller. The answer is always true or false.

In this page:

Equality and Inequality
Greater than and Less than
Greater than or Equal, and Less than or Equal
Relational Checks on Numbers
Relational Checks on Characters

Syntax

cpp

bool result = value1 == value2;  // also != > < >= <=

Equality and Inequality

== checks whether two values are equal and != checks whether they're different, and both always produce a boolean result (true or false) rather than the values themselves.

A very common beginner mistake is writing a single = instead of == inside a condition, which silently assigns instead of compares.

Example: Equality and Inequality

cpp

// Include std::cout and std::cin
#include <iostream>

// Program execution starts in main()
int main() {
	int a = 5, b = 3;
	// Print to the console with cout
	std::cout << (a == b) << std::endl;
	// Print to the console with cout
	std::cout << (a != b) << std::endl;
	// Return 0 to signal that the program finished successfully
	return 0;
}

Greater than and Less than

> and < test whether the left-hand value is strictly greater than or strictly less than the right-hand value, which is strict in the sense that equal values evaluate to false for both.

These are the basis for sorting logic and range checks throughout C++ code.

Example: Greater than and Less than

cpp

// Include std::cout and std::cin
#include <iostream>

// Program execution starts in main()
int main() {
	// Print to the console with cout
	std::cout << (5 > 3) << std::endl;
	// Print to the console with cout
	std::cout << (5 < 3) << std::endl;
	// Return 0 to signal that the program finished successfully
	return 0;
}

Greater than or Equal, and Less than or Equal

>= and <= extend > and < to also accept equality, so x >= 5 is true whenever x is 5 or anything larger.

Choosing between the strict and inclusive versions correctly is critical for avoiding off-by-one errors, especially in loop bounds and array index checks.

Example: Greater than or Equal, and Less than or Equal

cpp

#include <iostream>

int main() {
	int x = 5;
	std::cout << (x >= 5) << std::endl; // true: equal counts
	std::cout << (x <= 4) << std::endl;
	return 0;
}

Relational Checks on Numbers

Relational operators are what give if statements their decision-making power — an expression like if (score >= passingGrade) evaluates to true or false and determines which branch of code actually runs.

Nearly every piece of conditional logic in a real C++ program is built from combinations of these comparisons.

Example: Relational Checks on Numbers

cpp

// Include std::cout and std::cin
#include <iostream>

// Program execution starts in main()
int main() {
	int score = 75, passingGrade = 60;
	// Check whether score >= passingGrade
	if (score >= passingGrade) {
		// Print to the console with cout
		std::cout << "Passed" << std::endl;
	}
	// Return 0 to signal that the program finished successfully
	return 0;
}

Relational Checks on Characters

Comparing char values compares their underlying ASCII numeric codes, so a < b is true because a has a smaller code than b, and importantly, all uppercase letters have smaller codes than all lowercase letters, meaning Z < a is also true.

This ASCII-based ordering is why naive alphabetical sorting of mixed-case text can produce surprising results unless you normalize case first.

Example: Relational Checks on Characters

cpp

#include <iostream>

int main() {
	std::cout << ('a' < 'b') << std::endl;
	std::cout << ('Z' < 'a') << std::endl; // uppercase codes are smaller
	return 0;
}

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