Example: Enhanced Bill with Tax and Discount in C

// Enhanced Bill with Tax and Discount
#include <stdio.h>
#include <string.h> // Required for strcmp

int main() {
    // Step 1: Declare variables
    char customerName[50];
    char itemName[30];
    int qty;
    float price, itemTotal;
    float subtotal = 0.0;
    float taxRate = 0.10; // 10% tax
    float discountRate = 0.05; // 5% discount
    float taxAmount, discountAmount, totalPayable;
    char addMore = 'y';

    // Step 2: Get customer name
    printf("Enter Customer Name: ");
    fgets(customerName, sizeof(customerName), stdin);
    for (int i = 0; customerName[i] != '\0'; i++) {
        if (customerName[i] == '\n') {
            customerName[i] = '\0';
            break;
        }
    }

    // Step 3: Print bill header
    printf("\n--- Bill Statement ---\n");
    printf("Customer Name: %s\n", customerName);
    printf("----------------------------------------\n");
    printf("%-15s %-5s %-10s %-10s\n", "Item", "Qty", "Price", "Total");
    printf("----------------------------------------\n");

    // Step 4: Loop to get multiple item details
    while (addMore == 'y' || addMore == 'Y') {
        printf("Enter Item Name (or type 'done' to finish): ");
        fgets(itemName, sizeof(itemName), stdin);
        for (int i = 0; itemName[i] != '\0'; i++) {
            if (itemName[i] == '\n') {
                itemName[i] = '\0';
                break;
            }
        }

        if (strcmp(itemName, "done") == 0 || strcmp(itemName, "Done") == 0) {
            break; // Exit loop
        }

        printf("Enter Quantity for %s: ", itemName);
        scanf("%d", &qty);
        printf("Enter Price per unit for %s: ", itemName);
        scanf("%f", &price);
        while (getchar() != '\n'); // Clear input buffer

        itemTotal = qty * price;
        subtotal += itemTotal;

        printf("%-15s %-5d %-10.2f %-10.2f\n", itemName, qty, price, itemTotal);

        printf("Add another item? (y/n): ");
        scanf(" %c", &addMore);
        while (getchar() != '\n'); // Clear input buffer
    }

    // Step 5: Calculate tax, discount, and total payable
    taxAmount = subtotal * taxRate;
    discountAmount = subtotal * discountRate; // Discount applied before tax is common, but here after subtotal
    totalPayable = subtotal + taxAmount - discountAmount;

    // Step 6: Print final bill with tax and discount
    printf("----------------------------------------\n");
    printf("%-32s %-10.2f\n", "Subtotal:", subtotal);
    printf("%-32s %-10.2f\n", "Tax (%.0f%%):", taxRate * 100, taxAmount);
    printf("%-32s %-10.2f\n", "Discount (%.0f%%):", discountRate * 100, discountAmount);
    printf("----------------------------------------\n");
    printf("%-32s %-10.2f\n", "Total Payable:", totalPayable);
    printf("----------------------------------------\n");

    return 0;
}