Student Library

C++ Functions

2 min read

A function is one of the most useful code writing tools in programming!

We follow this syntax for creating functions.

dataType functionName () {
	// statements of your function
}

We can use functions to often simplify large blocks of code.
For example, we can write a function that displays a message in a console.

void hello () {
	cout << "Hello, I'm Emu Ootori!";
}

By calling this function in our main(), we execute the statement inside the hello() function.

void hello () {
	cout << "Hello, I'm Emu Ootori!";
}
 
int main () {
	hello(); // Outputs "Hello, I'm Emu Ootori!"
	return 0;
}

Function Arguments

A function can take in inputs as well.

These inputs that a function takes are called arguments.


Suppose that we want to display a number in the console using a function.

We can instead assign an argument num and initialize it as an integer like this.

void displayNum (int num) {
	cout << num << endl;
}

This way, if we do it like this, we can change the number we want to output as well.

int main () {
	displayNum(2); // Outputs "2"
	displayNum(5); // Outputs "5"
	displayNum(20); // Outputs "20"
	displayNum(69); // Outputs "69"
	return 0;
}

They can also take in multiple inputs.

We can have a function that adds two numbers.

void add (int num1, int num2) {
	int sum = num1 + num2;
	cout << "The sum of " << num1 << " and " << num2 << " is " << sum << endl;
}

However, for each argument we add, we separate our inputs with a comma.

int main () {
	add(1, 2); // Outputs "The sum of 1 and 2 is 3"
	return 0;
}

You can also other data types aside from int when assigning functions too.

void line (char lineCh) {
	for (i = 1; i <= 80; i++) cout << lineCh;
}

Note

When using strings as an argument in a function, make sure to use the char* data type.

void displayMessage (char* message) {
	cout << message << endl;
}
line()

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