Compute Powers and Exponents in C

Introduction

In this lab, you will learn how to compute powers and exponents in C programming. The lab covers two main steps: reading the base and exponent values from the user, and then calculating the power using either a manual loop or the built-in pow() function. By the end of this lab, you will have a solid understanding of how to perform power calculations in C, which is a fundamental operation in many mathematical and scientific applications.

Skills Graph

Read Base and Exponent

In this step, you will learn how to read the base and exponent values for calculating powers in a C program. We'll create a simple program that prompts the user to input these values.

First, let's create a new C file in the ~/project directory:

cd ~/project
nano power_calculation.c

Now, enter the following code to read base and exponent:

#include <stdio.h>

int main() {
    int base, exponent;

    // Prompt user to enter base
    printf("Enter the base number: ");
    scanf("%d", &base);

    // Prompt user to enter exponent
    printf("Enter the exponent: ");
    scanf("%d", &exponent);

    // Print the entered values
    printf("Base: %d\n", base);
    printf("Exponent: %d\n", exponent);

    return 0;
}

Let's compile and run the program:

gcc power_calculation.c -o power_calculation
./power_calculation

Example output:

Enter the base number: 5
Enter the exponent: 3
Base: 5
Exponent: 3

Code Explanation:

• scanf() function is used to read integer input from the user
• %d is the format specifier for integers
• &base and &exponent pass the memory addresses where input values will be stored
• The program simply reads and displays the base and exponent values

This step sets up the foundation for calculating powers by first obtaining the necessary input from the user.

Use a Loop or pow() Function

In this step, you will learn two methods to calculate powers in C: using a manual loop and using the built-in pow() function from the math library.

First, let's modify the previous power_calculation.c file to implement power calculation:

cd ~/project
nano power_calculation.c

Method 1: Using a Loop

#include <stdio.h>

int calculate_power_loop(int base, int exponent) {
    int result = 1;
    for (int i = 0; i < exponent; i++) {
        result *= base;
    }
    return result;
}

int main() {
    int base, exponent;

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

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

    int power_result = calculate_power_loop(base, exponent);

    printf("%d raised to the power of %d is: %d\n", base, exponent, power_result);

    return 0;
}

Method 2: Using pow() Function

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

int main() {
    int base, exponent;

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

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

    // Note: pow() returns a double, so we cast to int
    int power_result = (int)pow(base, exponent);

    printf("%d raised to the power of %d is: %d\n", base, exponent, power_result);

    return 0;
}

Compile the program with the math library:

gcc power_calculation.c -o power_calculation -lm

Example output:

Enter the base number: 2
Enter the exponent: 3
2 raised to the power of 3 is: 8

Code Explanation:

• Loop method manually multiplies the base by itself exponent times
• pow() function from math.h provides a built-in power calculation
• -lm flag is required to link the math library when compiling
• We cast pow() result to int to match our integer calculation

Print the Result

In this step, you will enhance the power calculation program to provide more detailed and formatted output, demonstrating different ways of presenting results in C.

Let's modify the power_calculation.c file:

cd ~/project
nano power_calculation.c

Add the following comprehensive code:

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

void print_power_result(int base, int exponent, int result) {
    // Basic print format
    printf("Basic Result: %d^%d = %d\n", base, exponent, result);

    // Formatted print with alignment
    printf("Formatted Result: %2d raised to the power of %2d equals %5d\n",
           base, exponent, result);

    // Scientific notation for larger numbers
    printf("Scientific Notation: %d^%d = %.2e\n", base, exponent, pow(base, exponent));
}

int calculate_power_loop(int base, int exponent) {
    int result = 1;
    for (int i = 0; i < exponent; i++) {
        result *= base;
    }
    return result;
}

int main() {
    int base, exponent;

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

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

    int power_result = calculate_power_loop(base, exponent);

    // Call function to print results
    print_power_result(base, exponent, power_result);

    return 0;
}

Compile the program:

gcc power_calculation.c -o power_calculation -lm

Run the program:

./power_calculation

Example output:

Enter the base number: 5
Enter the exponent: 3
Basic Result: 5^3 = 125
Formatted Result:  5 raised to the power of  3 equals   125
Scientific Notation: 5^3 = 1.25e+02

Code Explanation:

• print_power_result() demonstrates multiple printing formats
• Basic print shows simple calculation
• Formatted print uses width specifiers for alignment
• Scientific notation useful for large numbers
• %.2e displays number in scientific format with 2 decimal places

Summary

In this lab, you learned how to read the base and exponent values from the user, and then calculate the power using two different methods: a manual loop and the built-in pow() function. You implemented the loop-based power calculation function and the pow() function call, and then compared the results. This allowed you to understand the different approaches to computing powers and exponents in C programming.