Array in C#: Simple Interest Calculator

Introduction of the Lesson

Arrays are fundamental data structures in C# that allow programmers to store and manipulate multiple values efficiently using a single variable. In real-world applications, especially in finance and business systems, arrays are frequently used to manage collections of related data such as multiple clients, loan records, or investment values.

In this lesson, you will learn how arrays can be applied to create a Simple Interest Calculator. This example simulates a basic financial system where multiple principal amounts, interest rates, and time durations are processed to compute interest values. By using arrays, you can handle multiple transactions simultaneously, making your program more efficient and scalable.

This lesson integrates programming fundamentals with practical financial computation, helping you understand how software solutions are used in banking, lending, and financial tracking systems.

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Objectives

To ensure structured learning and measurable outcomes, this lesson follows the Outcome-Based Education (OBE) framework. The objectives are categorized into four key competencies:

Introductory Objective Statement

The objectives of this lesson are designed to progressively develop your knowledge and skills in using arrays within real-world financial applications. You will move from understanding the concept to applying it in building functional programs.

Understand

Explain the concept of arrays and how they store multiple values. Understand how arrays are used in financial computations such as interest calculation.

Learn

Learn how to implement arrays in C# to store principal amounts, interest rates, and time periods. Understand the formula for simple interest and how it is applied programmatically.

Practice

Practice writing C# programs that utilize arrays and loops to calculate simple interest for multiple entries. Develop confidence in handling multiple data inputs.

Apply

Apply the concept by creating scalable financial programs that compute and display interest values for multiple clients or transactions.

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Beginner-Friendly Source Code (With Namespace)

Instructions

1. Open Visual Studio Code.
2. Create a new C# console application.
3. Copy and paste the code below.
4. Run the program.
5. Observe how arrays are used to compute multiple interest values.

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Source Code

using System;

namespace FinancialArrayApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("=== Simple Interest Calculator ===");

            // Arrays for multiple clients
            double[] principal = { 10000, 5000, 15000 };
            double[] rate = { 0.05, 0.04, 0.06 };
            int[] time = { 2, 3, 1 };

            for (int i = 0; i < principal.Length; i++)
            {
                double interest = principal[i] * rate[i] * time[i];
                double totalAmount = principal[i] + interest;

                Console.WriteLine($"\nClient {i + 1}:");
                Console.WriteLine($"Principal: {principal[i]}");
                Console.WriteLine($"Interest: {interest}");
                Console.WriteLine($"Total Amount: {totalAmount}");
            }

            Console.ReadKey();
        }
    }
}

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Example Output

=== Simple Interest Calculator ===

Client 1:
Principal: 10000
Interest: 1000
Total Amount: 11000

Client 2:
Principal: 5000
Interest: 600
Total Amount: 5600

Client 3:
Principal: 15000
Interest: 900
Total Amount: 15900

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Lesson Summary

In this lesson, you explored how arrays can be effectively used in C# to handle multiple financial records within a single program. By implementing a Simple Interest Calculator, you learned how to store and process multiple values such as principal, rate, and time using arrays. The integration of loops allowed for efficient computation across multiple data sets, demonstrating how programming can simplify real-world financial tasks. These skills are essential in developing systems for banking, lending, and financial management, where handling bulk data accurately is critical.

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Multiple Choice Questions

1. What is the formula for simple interest?
   A. P + R + T
   B. P × R × T
   C. P × T
   D. R × T
2. Why are arrays used in this program?
   A. To store only one value
   B. To store multiple financial records
   C. To print output
   D. To stop execution
3. If principal = 2000, rate = 0.05, time = 2, what is the interest?
   A. 100
   B. 200
   C. 150
   D. 250
4. What will happen if the arrays have different lengths?
   A. Program works normally
   B. It may cause an error
   C. It improves performance
   D. It prints nothing
5. Why is using arrays beneficial in financial systems?
   A. Reduces data storage
   B. Handles multiple records efficiently
   C. Slows down computation
   D. Eliminates loops

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Exercises, Assessment, and Lab Exam

Introduction to Exercises

The following activities are designed to deepen your understanding of arrays and financial computations. These tasks will help you transition from basic coding to building more dynamic and interactive applications.

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Exercises

1. Modify the program to accept user input for principal, rate, and time.
2. Add more clients dynamically.
3. Display the highest interest earned.

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Assessment

1. Create a program that calculates compound interest using arrays.
2. Add input validation (e.g., prevent negative values).
3. Display total and average interest.

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Lab Exam

Task:
Develop a C# program that:

• Accepts data for 5 clients (principal, rate, time)
• Computes simple interest for each
• Displays:
  • Total interest earned
  • Highest interest
  • Client with the largest investment

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