# C++ Program to Find Largest of Three Numbers Using Functions

Howdy readers, today you will learn how to write a C++ program to find the largest of three numbers using functions.

The below program prompts the user to enter three numbers, then it computes the largest among them using a user-defined function.

The user-defined function uses comparison operators to find the largest number in the below program.

So, without any delay, letâ€™s begin this tutorial.

## C++ Program to Find Largest of Three Numbers Using Functions

C++ Program

```// C++ Program to Find Largest of Three Numbers Using Functions
#include <iostream>
using namespace std;

// User-defined function
int largestNumber(int a, int b, int c){
int max;
if (a >= b && a >= c){
max = a;
}
else if (b >= a && b >= c){
max = b;
}
else{
max = c;
}
return max;
}

int main(){
int num1, num2, num3, largest;

// Taking input
cout << "Enter the first number: ";
cin >> num1;
cout << "Enter the second number: ";
cin >> num2;
cout << "Enter the third number: ";
cin >> num3;

// Calling out function
largest = largestNumber(num1, num2, num3);

// Display result
cout << "Largest number is: " << largest << endl;

return 0;
}
```

Output

```Enter the first number: 18
Enter the second number: 30
Enter the third number: 27
Largest number is: 30
```

Explanation

```int largestNumber(int a, int b, int c){
int max;
if (a >= b && a >= c){
max = a;
}
else if (b >= a && b >= c){
max = b;
}
else{
max = c;
}
return max;
}
```

In this program, we have defined a function named `largestNumber` which passes three numbers as arguments and returns the greatest of them.

```    // Calling out function
largest = largestNumber(num1, num2, num3);
```

Then, we call out the custom function in the main function. This gives us the desired result. We store the largest number in the `largest` named variable.

```    cout << "Largest number is: " << largest << endl;
```

The largest number among the three is displayed on the screen using the `cout` statement.

## Conclusion

Today you learned how to write a C++ program to find the largest of three numbers using a function.

If you have any doubts regarding the tutorial, comment down your queries in the comment section.