C Functions
A function is a block of code which only runs when it is called.
You can pass data, known as parameters, into a function.
Functions are used to perform certain actions, and they are important for reusing code: Define the code once, and use it many times.
Predefined Functions
So it turns out you already know what a function is. You have been using it the whole time while studying this tutorial!
For example, main()
is a function, which is used to execute code,
and printf()
is a function; used to output/print text to the screen:
Create a Function
To create (often referred to as declare) your own function, specify the name of the function, followed by parentheses ()
and curly brackets {}
:
Syntax
void myFunction() {
// code to be executed
}
Example Explained
myFunction()
is the name of the functionvoid
means that the function does not have a return value. You will learn more about return values later in the next chapter- Inside the function (the body), add code that defines what the function should do
Call a Function
Declared functions are not executed immediately. They are "saved for later use", and will be executed when they are called.
To call a function, write the function's name followed by two parentheses ()
and a semicolon ;
In the following example, myFunction()
is used to print a text (the action), when it is called:
Example
Inside main
,
call
myFunction()
:
// Create a function
void myFunction() {
printf("I just got
executed!");
}
int main() {
myFunction(); // call the function
return 0;
}
// Outputs
"I just got executed!"
Try it Yourself »
A function can be called multiple times:
Example
void myFunction() {
printf("I just got executed!");
}
int main() {
myFunction();
myFunction();
myFunction();
return 0;
}
//
I just got executed!
// I just got executed!
// I just got executed!
Try it Yourself »