What is Function in C Programming? Types, Advantages | Intellipaat

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What is a Function in C Programming
Updated on 06th Jun, 23 6.8 K Views

In particular, the Input-Output Function, Main Function, and Pre-defined Function will be highlighted in this article as different categories of functions in the C programming language. It will also draw attention to the benefits that C language programmers get from employing these functions.


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Understanding Functions in C Language

A function in C is a chunk of code that performs a specified task. They are used to break down code into smaller, more manageable chunks that may then be called from other portions of a program to accomplish their unique duty. In C language, a function can take zero or more parameters and return a value or nothing at all.

Before a function can be used, it must be declared, and this declaration includes information like the function’s name, return type, and parameter types. Later in the program, with the actual code that does the task, the function is defined. Once defined, a function can be called from any portion of the program where it is visible. Functions are a fundamental notion in C programming that is frequently used in the development of larger, more complicated programs.

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Why are Functions necessary in C Programming?

Due to their potential to produce more effective, understandable, and manageable code, functions are a crucial tool in the world of C programming. Functions are used for a variety of things in C programming. Here are some of the main rationales as to why functions are required in C.

  • Code Organization – Functions help organize the code by dissecting complex programs into smaller, manageable chunks. In turn, this improves the readability, comprehension, and maintainability of the code.
  • Reusability – By breaking a program down into functions, it is possible to reuse the same code in other parts of the program, thus saving time and effort while reducing the likelihood of errors, as well.
  • Modular Programming – Functions can be thought of as modules that are each responsible for a certain purpose. This modular approach to programming makes it easier to test and troubleshoot the different components of a program.
  • Abstraction –  Functions allow us to abstract away the specifics of how a task is carried out. This allows us to concentrate on what the function does rather than how the function accomplishes it, in turn making the code more readable and understandable.
  • Encapsulation –  Functions enable the encapsulation of code and data, thus making them easier to manage and secure. We can prohibit other sections of the program from accessing or affecting the internal state of a function by masking implementation details behind a function interface.

Types of Functions in C Programming

Types of Functions in C Programming

The C programming language includes a variety of functions, which are enumerated below.

  • Main function – This function marks the start of any C program. It is a preset function that is first executed when a program is run. The main function may call other functions to execute specific tasks.
Example: int main(void) {
    // code to be executed
    return 0;
  • Library functions –  These are preset functions that are already available in the C library. They perform particular tasks including mathematical computations, input/output activities, and string operations. In C programming, library functions include printf(), scanf(), sin(), cos(), and strlen().
  • User-defined functions – In the C language, a user-defined function is one that is created by the programmer to perform a specific task. The programmer specifies the name, return type, and parameters of the function, while the code of the function is defined within curly braces.
  • Input-output function –  In C programming, an input-output function is one that either takes user input or sends data to the user. These capabilities allow programmers to interface with users as well as receive or provide information. Printf(), scanf(), getchar(), and putchar() are examples of I/O routines. These features are necessary to develop interactive programs that respond to user interaction.

Pre-Defined Functions in C Language

The C language has been equipped with a large number of built-in functions, which are easily available in the C library. These pre-programmed functions are engineered to carry out specific actions, including arithmetic computations, input/output procedures, and textual manipulations. Mentioned below are some of the pre-programmed functions in the C language.

  • printf() – This function is a vital tool in the C language, as it provides output data in an ordered and formatted manner so that they can be easily understood by end users through the console or terminal. It can also display other kinds of data including variables and strings. This function is frequently used in C programming, which emphasizes its importance to programmers for creating responsive and interactive software systems.
  • scanf() – With the scanf() function, the programmers can assign user input to variables for further use in the program. In C programming, this function is used to read input data from the user.
  • sin() – In the C language, sin() is a mathematical function that is used to calculate the sine of an angle in radians. It is a part of the math.h library and can be used to perform trigonometric calculations in a C program.
  • cos() – This function is a part of the math.h library, as well, and it can be used in C programs to calculate trigonometric computations. This mathematical function calculates the cosine of an angle in radians.
  • strlen() – This built-in function in the C language calculates the length of given strings or character arrays, excluding the null character. It is included in the string.h library and can be used to count the characters in a string.

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Input-Output Functions in C Programming

Input-Output Functions in C Programming

Users can read user input and see data displayed using input-output functions. Both engaging with users and processing data depend on these features. As previously mentioned, the C header file includes input and output functions like ‘scanf()’ for input and ‘printf()’ for output.   

Let’s examine some of the most common input functions.

  • printf – To print formatted output to the screen or to a file, use the printf` function. In addition to one or more format specifiers that specify how the data should be formatted, it also accepts a string as its first parameter. When the function is called, the format specifiers serve as placeholders for the associated data. Several of the most popular format specifiers include
For integers, use %d.
For floating-point numbers, use %f.
For characters, use %c.
For strings, use %s

For instance, the code snippet below makes use of printf to display the value of an integer variable.

int num = 23;
printf("The value of num is %d\n", num);

The following text will appear on the screen as a result

The value of num is 23

  • scanf – Use the scanf function to read data from a file or the keyboard. It accepts a string as its first parameter, then one or more format specifiers that specify how to read the data. Similar to the format specifiers used by printf, instead of placeholders, they specify the kind of data to be read.

As an illustration, the code snippet below makes use of scanf to read an integer value from the keyboard

int num;
printf("Enter a number: ");
scanf("%d", &num);
printf("You entered %d\n", num);

This program reads the user’s entered number from the keyboard, prompts them to enter a number, and then writes it back on the screen.

Let’s now look at some of the most used output routines.

  • getchar() – A single character can be read from the keyboard using the getchar function. It does not require any input and gives back an integer value that is the character’s read ASCII code.

The ability to wait for user input before continuing execution makes this function helpful for interactive programs. Getchar() is used to read a single character from the user, to put it simply. This is how its syntax looks

int getchar(void);

For instance, the following line of code reads a single character from the keyboard and outputs its ASCII code.

int ch;
printf("Enter a character: ");
ch = getchar();
printf("The ASCII code of %c is %d\n", ch, ch);

This program asks the user to enter a character, then reads the character from the keyboard and prints its ASCII code.

  • putchar() – This C standard library function outputs a single character to the standard output stream, often the console, and then returns the character as an integer value.

To write a single character to the screen or a file, use the putchar function. It just needs one argument, which is the character’s ASCII code. The syntax is as follows

int putchar(int c);

For example, the following code snippet uses putchar to print the characters ‘S’, ‘p’, ‘a’, ‘r, ‘d’, ‘n’ to the screen


This program prints the word “Spardn” to the screen when it runs.

Main Functions in C Programming

In C, even if you don’t use user-defined functions or a library, you must use the main function, as it is the first function that is executed when the program is run. The main function can call other functions to perform specific tasks. The exit status of a program is determined by the main function’s return of an integer value to the operating system.

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Creating User-Defined Functions in C Language

Creating User-Defined Functions in C Language

User-defined functions, as the name suggests, are custom functions created by the user or programmer, according to their own need, to perform specific tasks. To create a user-defined function in the C language, the steps given below need to be followed.

  • Function Declaration – This provides the compiler with information about the function’s name, return type, and parameters.
  • Function Call –  Call the function in your program to execute the code inside the function body. To call a function, you need to write the name of the function followed by its arguments, which are enclosed in parentheses.
  • Function Definition –  This defines the function by providing the code that performs the task.

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Advantages of Functions in C Language

Functions in the C language offer numerous benefits, thus making them an indispensable tool for any programmer. The following are some key advantages of functions:

  • Reusability –  The same function can be reused multiple times, thus avoiding the duplication of code.
  • Modularity  A large program can be divided into smaller modules (functions) that carry out well-defined tasks, which makes the program easier to write, debug, and maintain.
  • Abstraction –  Functions help hide the underlying implementation details. This way, the caller of the function knows just the interface and not how the task is performed internally.
  • Testing –  It is easier to test functions separately. This helps isolate any bugs and fix them before integrating the functions into the full program.

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Functions are a fundamental notion in C programming. They provide a reusable tool for completing repetitive activities. Functions also help organize the code into smaller, more manageable chunks, thus providing a level of abstraction that makes complex programs easier to understand and deal with. The C programming language offers various kinds of functions, including library functions, user-defined functions, and main functions. The input/output functions are used to read user input and display output to the user. Predefined functions are already present in the C library and can be used to execute specified tasks.

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