In this tutorial, you will learn how to write a C program to find greatest of three numbers. We will see three programs: In the first program we will use if statement, second program if..else statement and in third program we will use nested if..else statement to find the greatest number.
Example 1: Program to find largest number using if statement
In this program, we are using if statement. The steps followed in this program are:
1. User is asked to enter three numbers one by one. The program store these numbers into three variables num1
, num2
and num3
using scanf() function.
2. Program compares num1
to other two variables num2
& num3
and if num1
is grater than both of these numbers then print num1
is the largest number.
3. Similarly compares num2
with num1
& num3
and if greater print num2
is the largest number.
4. Similar to step 2 and 3, compare num3
with num1
and num2
and if greater print num3
is the largest number.
#include <stdio.h>
int main() {
double num1, num2, num3;
printf("Enter first number: ");
scanf("%lf", &num1);
printf("Enter second number: ");
scanf("%lf", &num2);
printf("Enter third number: ");
scanf("%lf", &num3);
// if num1 is greater than num2 & num3, num1 is the largest
if (num1 >= num2 && num1 >= num3)
printf("%lf is the largest number.", num1);
// if num2 is greater than num1 & num3, num2 is the largest
if (num2 >= num1 && num2 >= num3)
printf("%lf is the largest number.", num2);
// if num3 is greater than num1 & num2, num3 is the largest
if (num3 >= num1 && num3 >= num2)
printf("%lf is the largest number.", num3);
return 0;
}
Output:
Example 2: Program to find largest number using if..else statement
#include <stdio.h>
int main() {
double num1, num2, num3;
printf("Enter first number: ");
scanf("%lf", &num1);
printf("Enter second number: ");
scanf("%lf", &num2);
printf("Enter third number: ");
scanf("%lf", &num3);
if (num1 >= num2 && num1 >= num3)
printf("%lf is the largest number.", num1);
else if (num2 >= num1 && num2 >= num3)
printf("%lf is the largest number.", num2);
// if both the above conditions are false then
// num3 is the largest number
else
printf("%lf is the largest number.", num3);
return 0;
}
Output:
Enter first number: 10 Enter second number: 50 Enter third number: 1 50.000000 is the largest number.
Example 3: Program to find largest number using nested if..else
#include <stdio.h>
int main() {
double num1, num2, num3;
printf("Enter first number: ");
scanf("%lf", &num1);
printf("Enter second number: ");
scanf("%lf", &num2);
printf("Enter third number: ");
scanf("%lf", &num3);
if (num1 >= num2) {
if (num1 >= num3)
printf("%.2lf is the largest number.", num1);
else
printf("%.2lf is the largest number.", num3);
}
else {
if (num2 >= num3)
printf("%.2lf is the largest number.", num2);
else
printf("%.2lf is the largest number.", num3);
}
return 0;
}
Output:
Enter first number: 100 Enter second number: 999 Enter third number: 1202 1202.00 is the largest number.
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