C Program: Calculating compound interest with User input Loop

C Do-While Loop: Exercise-11 with Solution

Write a C program that calculates the compound interest for a given principal amount, interest rate, and time period. Use a do-while loop to allow the user to input values multiple times.

Sample Solution:

C Code:

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

int main() {
    double principal, rate, time, compoundInterest;
	int flag;

    do {
        // Prompt the user to enter principal amount, interest rate, and time period
        printf("Input principal amount: ");
        scanf("%lf", &principal);

        printf("Input annual interest rate (as a percentage): ");
        scanf("%lf", &rate);

        printf("Input time period (in years): ");
        scanf("%lf", &time);

        // Check if the entered values are valid
        if (principal <= 0 || rate < 0 || time <= 0) {
            printf("Please input valid positive values for principal, interest rate, and time.\n");
            continue;  // Restart the loop for new input
        }

        // Convert interest rate from percentage to decimal
        rate /= 100;

        // Calculate compound interest
        compoundInterest = principal * pow(1 + rate, time) - principal;

        // Print the calculated compound interest
        printf("Compound Interest: %.2lf\n", compoundInterest);

        // Ask the user if they want to calculate again
        printf("Want to calculate compound interest again? (1 for Yes, 0 for No): ");
        scanf("%d", &flag);

    } while (flag == 1);

    return 0;  // Indicate successful program execution
}

Sample Output:

Input principal amount: 10000
Input annual interest rate (as a percentage): 4
Input time period (in years): 5
Compound Interest: 2166.53
Want to calculate compound interest again? (1 for Yes, 0 for No): 1
Input principal amount: 5000
Input annual interest rate (as a percentage): 3.9
Input time period (in years): 8
Compound Interest: 1790.38
Want to calculate compound interest again? (1 for Yes, 0 for No): 0

Explanation:

Here are key parts of the above code step by step:

• double principal, rate, time, compoundInterest; int flag: Declares variables to store principal amount, interest rate, time period, and compound interest. Using 'flag' ask the user if they want to calculate again.
• do { ... } while (time == 1);: Uses a do-while loop to allow the user to input values multiple times.
• principal amount: ");, scanf("%lf", &principal);, etc.: Prompts the user to input principal amount, interest rate, and time period.
• if (principal <= 0 || rate < 0 || time <= 0) { ... }: Checks if the input values are valid. If not, prompts the user to enter valid positive values.
• rate /= 100;: Converts the interest rate from percentage to decimal.
• compoundInterest = principal * pow(1 + rate, time) - principal;: Calculates compound interest using the compound interest formula.
• printf("Compound Interest: %.2lf\n", compoundInterest);: Prints the calculated compound interest.
• printf("Do you want to calculate compound interest again? (Enter 1 for Yes, 0 for No): ");, scanf("%d", &time);: Asks the user if they want to calculate again. If the user enters 1, the loop continues; otherwise, it exits.
• return 0;: Indicates successful program execution.

Flowchart:

C Programming Code Editor:

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