Functions in C Programming

Functions in c programming; In this tutorial, you will learn everything about functions in C programming with the help of examples.

Functions in C Programming

• What is a function of C
• Types of function in C
• Syntax of a function in C
• Declare and Call Function in C
• Advantages of Functions in C
• Example 1 – C Program to Find the Area of a Rectangle Using Functions
• Example 2 – C Program to Find the Area of a Circle Using Functions

What is a function of C

A function is a set of statements enclosed by {}, that performs a specific task.

Types of function in C

There are two types of functions in C programming:

1. Library Functions: are the functions which are declared in the C header files such as scanf(), printf(), gets(), puts(), ceil(), floor() etc.
2. User-defined functions: are the functions which are created by the C programmer, so that he/she can use it many times. It reduces the complexity of a big program and optimizes the code.

Syntax of a function in C

Syntax of function in c programming; as follows:

return_type function_name (argument list)
{
    Set of statements – Block of code
}

Declare and Call Function in C

Use the following syntax to declare and call a function in c programming; as follows:

#include <stdio.h>
void functionName()
{
    ... .. ...
    ... .. ...
}

int main()
{
    ... .. ...
    ... .. ...

    functionName();
    
    ... .. ...
    ... .. ...
}

Advantages of Function in C

There are main advantages of functions in C programming:

• The program will be easier to understand, maintain and debug.
• Reusable codes that can be used in other programs.
• To avoid rewriting same logic/code again and again in a program.
• Can call a C function any number of times from any place in a program.
• Reusability is the main achievement of C functions.
• A large program can be divided into smaller modules. Hence, a large project can be divided among many programmers.

Example 1 – C Program to Find the Area of a Rectangle Using Functions

Use the following steps to write a C program using a user-defined function to find the area of a rectangle; as follow:

• Create user-define function, which name findArea().
• And in findArea() function, pass width & length of area.
• Find the area of a rectangle using this formula length * width and return the result.
• Take input length and width of the rectangle in the program.
• Call findArea() function with width & length and store result in variable.
• Finally print area of reactangle

#include<stdio.h>

// function to find ara of rectangle
// function definition
float findArea(float l, float b)
{
  float area;
  area = l * b;
  return area; //return statement
}

int main()
{
  float length, width, result;

  printf("Please enter length of the rectangle: ");
  scanf("%f",&length);
  printf("Please enter width of the rectangle: ");
  scanf("%f",&width);

  result = findArea(length, width); //function calling
  printf("Area of rectangle = %.2f\n",result);

  return 0;
}

Output of the above c program; as follow:

Please enter length of the rectangle: 10
Please enter width of the rectangle: 55
Area of rectangle = 550.00

Example 2 – C Program to Find the Area of a Circle Using Functions

Use the following steps to write a C program with a user-defined function to find the area of a circle; as follow:

• Create user-define function, which name circleArea().
• And in circleArea() function, pass radious of area.
• Find the area of a circle using this formula 3.14 * r * r and return the result.
• Take input radious of circle in the program.
• Call circleArea() function with radious and store result in variable.
• Finally print area of circle.

#include<stdio.h>

// function definition
float circleArea(float r)
{
  float area = 3.14 * r * r;
  return area; // return statement
}

int main()
{
  float radius, area;

  printf("Enter the radius of the circle: ");
  scanf("%f", &radius);

  area = circleArea(radius); //function calling
  printf("Area of circle = %.2f\n",area);

  return 0;
}

Output of the above c program; as follow:

Enter the radius of the circle: 25
Area of circle = 1962.50