• C Program to Find the Largest Number Among Three Numbers

    Welcome to this blog post where we will discuss and learn how to write a C program to find the largest number among three numbers using a function. This program is a fundamental concept in programming and will help you understand the basics of functions and conditional statements in the C programming language. Whether you are new to programming or have some prior experience, this post will provide step-by-step guidance to solve this problem.


    Have you ever wondered how computers can determine the largest number among a set of numbers? Well, it’s all about using the power of programming. In this program, we will introduce the concept of functions in C and demonstrate their use in finding the largest number among three given numbers.

    The purpose of this post is to explain the program in a clear and concise manner, ensuring that even beginners can easily follow along. By the end of this blog post, you will have a solid grasp of using functions and conditional statements to solve this problem.

    So, without further ado, let’s dive into the details!

    What is a Function?

    Functions serve as blocks of reusable code that perform specific tasks. They allow you to break down complex programs into smaller, manageable pieces. In C, a function consists of a function declaration and a function definition.

    Function Declaration

    A function declaration specifies the function’s name, return type, and any parameters it requires. In our case, we will declare a function called findLargestNumber that takes three integer parameters.

    Function Definition

    The function definition includes the actual code that executes when the function is called. In our code, the findLargestNumber function will compare the three numbers and return the largest among them using conditional statements.

    Writing the C Program

    To write the program, we will follow these steps:

    1. Include the necessary header files.

    2. Declare the findLargestNumber function.

    3. Implement the function to find the largest number.

    4. Write the main function to input the numbers and call the findLargestNumber function.

    5. Display the result.

    Let’s break down these steps and discuss them in detail.

    Step 1: Include the necessary header files

    The first step is to include the necessary header files in our program. In this case, we need the stdio.h header file to work with input and output functions.

    #include <stdio.h>

    Step 2: Declare the findLargestNumber function

    Next, we need to declare the findLargestNumber function. The function declaration specifies its return type and the parameters it takes. In our case, this function will return an integer and take three integer parameters representing the numbers to compare.

    int findLargestNumber(int num1, int num2, int num3);

    Step 3: Implement the findLargestNumber function

    After declaring the function, we can implement it to find the largest number among the three given numbers. This function will use conditional statements (if and else) to compare the numbers and determine the largest one.

    Here’s how the implementation looks:

    int findLargestNumber(int num1, int num2, int num3) {
        int largest;
        if (num1 >= num2 && num1 >= num3) {
            largest = num1;
        } else if (num2 >= num1 && num2 >= num3) {
            largest = num2;
        } else {
            largest = num3;
        return largest;

    Let’s understand the code logic a bit. We start by initializing a variable largest to hold the largest number. Then, using conditional statements, we compare num1 with num2 and num3. If num1 is greater than or equal to both num2 and num3, it is considered the largest. Similarly, we compare num2 with num1 and num3, and num3 with num1 and num2 to find the largest number.

    Step 4: Write the main function

    The main function serves as the entry point of our program. Here, we will take input from the user for the three numbers and display the largest number by calling the findLargestNumber function.

    int main() {
        int num1, num2, num3;
        printf("Enter three numbers: ");
        scanf("%d %d %d", &num1, &num2, &num3);
        int largest = findLargestNumber(num1, num2, num3);
        printf("The largest number is %d\n", largest);
        return 0;

    In the main function, we declare three integer variables num1, num2, and num3 to store the user input. We then prompt the user to enter the three numbers using the printf function and read them using the scanf function.

    Next, we call the findLargestNumber function and pass the three input numbers as arguments. The function returns the largest number, which we store in the largest variable. Finally, we use the printf function again to display the largest number.

    Step 5: Display the result

    The last step is to display the result, which we have already done in the previous step. The printf function is used to print the largest number.

    Running the Program

    To run the program, you need to compile and execute it. Save the code in a file with a .c extension, such as largest_number.c. Open a terminal or command prompt and navigate to the directory where the file is saved.

    Compile the code using a C compiler, such as GCC, by running the following command:

    gcc -o largest_number largest_number.c

    This will generate an executable file named largest_number. Execute the program by running the following command:


    Now, you can enter the three numbers when prompted, and the program will display the largest number.


    In this blog post, Finally, we have learned how to write a C program to find the largest number among three numbers using a function. We discussed the concepts of functions, function declaration, function definition, and conditional statements.

    By breaking down the program into smaller steps, we were able to solve the problem of finding the largest number in a structured manner. This approach not only helps in understanding the program better but also allows us to reuse the code whenever needed.

    Remember, practice is key to mastering any programming concept. I encourage you to try different variations of the program, explore edge cases, and experiment with different inputs. This will solidify your understanding and improve your problem-solving skills.

    If you want to delve deeper into C programming, there are countless resources available online, including tutorials, books, and practice exercises. Keep exploring, keep coding, and enjoy your programming journey!


    Happy coding!