Billing System Program in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

#include <stdio.h>
int main() {
    char p[20]; float price; int qty;
    scanf("%s %f %d", p, &price, &qty);
    float total = price * qty;
    if (qty > 5) total *= 0.9;
    printf("Bill: %.2f", total);
}

C Output

Input:
Pen 10 6
Output:
Bill: 54.00

C++ Program

#include <iostream>
using namespace std;
int main() {
    string p; float price; int qty;
    cin >> p >> price >> qty;
    float total = price * qty;
    if (qty > 10) total *= 0.85;
    cout << "Bill: " << total;
}

C++ Output

Input:
Notebook 20 12
Output:
Bill: 204

JAVA Program

import java.util.*;
public class Main {
    public static void main(String[] a) {
        Scanner s = new Scanner(System.in);
        String p = s.next(); float price = s.nextFloat(); int qty = s.nextInt();
        float total = price * qty;
        if (qty > 3) total *= 0.95;
        System.out.printf("Bill: %.2f", total);
    }
}

JAVA Output

Input:
Bottle 50 4

Output:
Bill: 190.00

Python Program

p, pr, q = input().split(); pr, q = float(pr), int(q)
t = pr * q; t *= 0.9 if q > 8 else 1
print("Bill:", round(t, 2))

Python Output

Input:
Towel 25 10

Output:
Bill: 225.0

In-Depth Explanation

Example

When a customer purchases 6 pens costing ₹10 each, the bill is ₹60. As the number is greater than 5, there is a discount of 10%:

₹60 × 0.9 = ₹54. Therefore, the bill amounts to ₹54.

In the Java version, purchasing 4 bottles costing ₹50 each amounts to ₹200. A 5% discount is applicable:

₹200 × 0.95 = ₹190.

Real-Life Analogy

Consider a stationery store. If you purchase more than 5 products, you are offered a discount. The store computes total cost by multiplying quantity with unit price and adjusts it if you are eligible for a discount. That's what this program mimics.

Why It Matters

This program teaches dynamic billing — a term applied everywhere:

Retail stores

E-commerce websites

Restaurant billing

Inventory systems

It not only teaches multiplication of quantity and price but also conditional billing rules, such as discounts depending on quantity.

Learning Insights

You'll learn:

Arithmetic operations in programs

Applying if conditions to apply rules

Real billing logic in the real world

Input parsing and output formatting

Writing shortest working versions of actual applications

Every language parses input and outputs differently, but the billing logic is the same — granting you cross-language expertise in applying logic to real-world simulations.

Interview & Real-World Relevance

Interviewers usually ask billing system programs to verify:

Arithmetic accuracy

Conditional logic

Handling of edge-cases (such as no discount for small orders)

Output formatting (such as 2-decimal billing)

In actual real-world projects, this logic is found in:

Supermarket checkout counters

Online shopping product ordering systems

Point-of-sale (POS) applications

Inventory or invoice systems

One of the best entry-level programming exercises to grasp multiplication, conditional discounts, and user input is a billing system. This concise, real-life sample gets you ready for job interviews, coding competitions, and real-world app development. Whether creating for a store, kiosk, or e-commerce site, the logic in here lays the groundwork for real-time price calculation and payment processing.