Defining and Calling Functions in C Programming

In the world of programming, functions play a vital role in structuring and organizing our code. They allow us to break down complex problems into smaller, more manageable tasks, making our code more understandable, reusable, and modular. In C programming, functions hold significant importance, and understanding how to define and call them is essential. So, let's dive into the world of functions in C!

Defining Functions

A function in C consists of several components, such as the return type, name, parameters, and the body. The general syntax for defining a function is as follows:

return_type function_name(parameter_type parameter1, parameter_type parameter2, ...) {
    // Function body
  • return_type: It defines the data type of the value that the function returns after its execution. It can be any valid C data type, such as int, float, char, void, etc. In case the function doesn't return any value, we use void as the return type.

  • function_name: It is the name given to the function, and it should follow the C identifier rules. The name should be meaningful and self-explanatory, reflecting the purpose of the function.

  • parameter_type: These are input values passed to the function. They can be variables or constants of any valid C data type, separated by commas. If the function doesn't require any input, we can leave the parameter list empty or use void keyword.

  • function_body: It consists of a series of statements enclosed within curly brackets that define the operations to be performed when the function is called.

Let's take an example of a simple function that calculates the square of a given number:

int square(int number) {
    int result = number * number;
    return result;

This function takes an integer parameter number and returns an integer (int) value. The body multiplies the number by itself and assigns the result to the result variable. Finally, the return statement returns the calculated result.

Calling Functions

Once we have defined a function, we can call it from any other part of our code to execute its statements and obtain the desired output. To call a function, we use the function name followed by parentheses, providing the necessary arguments (if any).

In our previous example, to call the square function and print the result, we can do the following:

int main() {
    int number = 5;
    int sqr = square(number);
    printf("Square of %d is %d", number, sqr);
    return 0;

Here, we invoke the square function and pass the number variable as an argument. The returned value is stored in the sqr variable, and we then use printf to display the computed result.


Functions are the building blocks of complex programs, enabling us to write clean, structured, and reusable code. In C programming, understanding how to define and call functions is crucial for effective program design. By following the syntax guidelines and utilizing appropriate return types, function names, and parameters, we can create modular and efficient code that simplifies problem-solving and enhances code maintainability.

© NoobToMaster - A 10xcoder company