In this blog post, we learn how to write a C program to calculate the power of a number?. We will write the C program to calculate the power of a number using the loop and arithmetic operators. Write the C program to calculate the power of a number using pow(x,n). Here we will write C function to calculate the power of a number. How to write C program to find power of a number using recursion.

Let see an example,

Input : data = 2, n = 3
Output : 8


Input : data = 7, n = 2
Output : 49

C program to compute the power of a number:

Below C program works only if the exponent is a positive integer. The program takes two integers from the user (base number and exponent) and calculates the power using loop and multiplication operator.

#include <stdio.h>

int main()
{
    int base,exponent;
    long long result = 1;

    printf("Enter base: ");
    scanf("%d", &base);

    printf("Enter exponent: ");
    scanf("%d", &exponent);

    if(exponent >= 0)
    {
        while(exponent--)
        {
            result *= base;
        }
        printf("Result = %lld",result);
    }
    else
    {
        printf("Enter positive exponent\n");
    }

    return 0;
}

Output:

Enter base: 2
Enter exponent: 4
Result = 16

Code Analysis:

1. After the first iteration, the value of the result will result = 1 * 2= 2.
2. After the second iteration, the value of the result will result = 2 * 2= 4.
3. After the third iteration, the value of the result will result = 4 * 2= 8.
4. After the fourth iteration, the value of the result will result = 8 * 2= 16.

Calculating power using the recursive function in C:

Below C program used to calculate powers using the recursion. Here exponent could be positive or negative integer number.

#include<stdio.h>

float power(float base, int exponent)
{
    float temp;
    if( exponent == 0)
    {
        return 1;
    }
    temp = power(base, exponent/2);
    if (exponent%2 == 0)
    {
        return temp*temp;
    }
    else
    {
        if(exponent > 0)
        {
            return base*temp*temp;
        }
        else
        {
            return (temp*temp)/base;
        }
    }
}

int main()
{
    double base;
    int exponent;

    printf("Enter base: ");
    scanf("%lf", &base);

    printf("Enter exponent: ");
    scanf("%d", &exponent);

    printf("%.2f^%d = %.2f", base, exponent, power(base, exponent));

    return 0;
}

Output 1:

Enter base: 10
Enter exponent: 2
10.00^2 = 100.00

Output 2:

Enter base: 4
Enter exponent: -1
4.00^-1 = 0.25

Calculating power using the pow() function in C:

In the below program, we will calculate powers using the pow() function. You must include math.h header file before using the pow() function.

#include<stdio.h>
#include<math.h>

int main()
{
    double base, exponent;

    printf("Enter base: ");
    scanf("%lf", &base);

    printf("Enter exponent: ");
    scanf("%lf", &exponent);

    printf("%.2f^%.2f = %.2f", base, exponent, pow(base, exponent));

    return 0;
}

Output:

Enter base: 10
Enter exponent: 4
10.00^4.00 = 10000.00

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