A Detailed Guide To Functions In C Programming

C language can be used to prepare well-structured functions that can help optimise our code. With the help of functions, we can optimise our problem statement by dividing it into smaller forms.

Here, we will provide you with a beginner-level introduction to the use of functions in C programming, which can help you learn functions quickly. You will learn how to use functions in your code and make your code effective. Read the complete article to know more.

Table of Contents

What Are Functions In C Programming

A function in C Programming is a defined set of statements that, when called, executes a specific task. It serves as a fundamental building block, encapsulating code to enhance modularity and readability.

Functions are user-defined blocks of statements specially designed to execute a specific task. It can be called directly or indirectly in your program. Function calls help you avoid writing the same piece of code again and again. As a result of using functions in C programming, our code looks less complex and highly structured.

Functions In C Programming

return_type function_name(parameter list) {

// function code to be executed

return value; /// not required in case of void data types.

}

In the above table, let us understand the elements used in the function syntax.

return_dataType: It is used to specify the data type of value which will be returned by the function at last.

function_name: Giving a name to our function is important while calling the function whenever necessary.

parameter_list: There can be one parameter or more than one parameter in a function. They are used to access the values provided when the users call them.

Body: This is where we write the code to help our function perform the intended task.

return value: This is used to return a value that our function obtains after executing the code inside.

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Types of Functions In C Programming

There are mainly two types of functions in C programming.

1. Standard Library Function

These functions are predefined functions in C language. They can be called inside our program by using preprocessors in C.

Some of the commonly used standard library functions are printf (), scanf(), stdio.h, sqrt(), etc. Let us check outheck an example of standard library functions in C programming.

Functions in C programming

#include <stdio.h>

#include <math.h>

int main() {

double number, squareRoot;

// Input a number from the user

printf(“Enter a number: “);

scanf(“%lf”, &number);

// Calculate the square root using sqrt() function

squareRoot = sqrt(number);

printf(“Square root of %.2lf = %.2lf\n”, number, squareRoot);

return 0;

}

Output

Square Root of 16 = 4

2. User-Defined Functions

As the name itself suggests, these functions are prepared by the users to execute a specific task. These functions are used to execute specific tasks, which are defined by the end users. It can be called inside a function or main function. Let us check the basic structure of User defined functions in C programming.

Functions in C programming

#include <stdio.h>

int fun()

{

//code

return value;

}

int main()

{

Int x = fun();

return x;

}

Remember, our program starts executing from the main function() and it calls a user defined function when it enters the main function.

Like in the table above, the code will start its execution from the main function, where it will see fun() function being called. Now, the code will jump to the user defined function fun() and return the executed value. We can call a function any number of times.

Important Terms in Functions in C programming

There are three major terms to be used while declaring a function in C programming.

Function Declaration: The function declarations are used to tell compiler the data type, name, and return type of function.
Function definition: Function definition contains the statements that will be executed when we call our function inside our program.
Function Call: You can call a function using the function name and the parameters anytime in your program. However, always use the same data type as present while declaring the function.

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Important Points For Functions In C Programming

Let us check out some of the important points that we must keep in mind while using functions in C programming.

Functions declaration should be completed before they are used inside our program.
We can declare a function without writing the parameter. It is optional. You can define the parameters while defining your function.
Always use the same data type and order that were used while declaring the function. The data types must not differ, as it can create compilation errors during function calls.
Always remember that your function should return only one value at the time of execution.

Example of Functions in C Programming

Let us check out a very easy and commonly used problem statement to understand the use of functions. Here, we need to calculate the factorial of a given number in C programming. Let us check the implementation.

Factorials in C Programming

// C program to find the factorial of a given number

#include <stdio.h>

unsigned int factorial (unsigned int n)

{

if (n == 1)

{

return 1;

}

return n * factorial (n – 1);

}

// Driver code

int main()

{

int num = 7;

printf (“Factorial of %d is %d”, num, factorial(num));

return 0;

}

We are using the function factorial (int num) to declare a user defined function that will calculate the factorial of a number using the recursive approach.

Important Header Files in C Programming

Let us check some of the most important header files used in C language.

Header Files in C programming
Header File	Description
stdio.h	The input/output header file contains all the library functions related to input and output operations.
conio.h	It is the console I/O file and contains library functions for console input/output operations.
string.h	This is the string header file that contains functions related to working with strings.
stdlib.h	The standard library consists of all general functions.
math.h	It is the math header file and contains all library functions related to math operations.
time.h	This header file consists of all the time-related functions
ctype.h	The ctype.h file includes all character handling functions.
stdarg.h	This header file consists of all the variable argument functions.
signal.h	The signal.h file contains all the signal handling functions.
setjmp.h	All the jump functions are declared in this header file.
locale.h	All the locale-related functions are defined in the locale header file.
errno.h	The errno.h header file has all the error handling functions.
assert.h	The assert.h file has all the functions used for diagnostic.

Why We Need Functions in C Programming

Let us check out some of the major benefits of using functions in our code.

Functions help us reuse our code and avoid redundancy by writing the same code many times in the same program.
It makes our code manageable and easy to understand.
With the help of functions, we break a complex problem into smaller modules.
It makes debugging easy.

Functions in C Programming FAQs

What are functions in C programming?

Functions are user-defined blocks of statements specially designed to execute a specific task. It can be called directly or indirectly in your program.

What are three main aspects of functions in C?

The three main aspects of Functions in programming are declaration, definition, and function call. Check out the article for more detail.

What are four types of function based on the arguments?

The four types of functions on the basis of arguments are:

Function with no arguments and not return values.
Functions with no arguments and one return value.
Functions with arguments and no return value.
Functions with arguments and one return value.