Decision Structures - If-Then-Else

Introduction

This topic introduces you to some fundamental coding practices for decision structure. There are several variations:

• If-Then
• If-Then-Else
• Nested If-Then-Else
• If-Else If

Demo Problem

To demonstrate a decision structure, you will create a console application that determines the highest and smallest number from three inputted values.

Input Variables

You will need three numeric (integer data type) variables:

• number1
• number2
• number3

Output Variables

You will need two numeric (integer data type) variables:

• highest
• smallest

User Input

You will need the following code to get user input for this problem:

Process Steps

The logic to solve this problem is shown below:

1. Compare number to number2; find the highest and smallest of the first two numbers:
   
   In this step we are not concered with the value of number3, that will come soon.
2. Now compare the highest, which was determined above, with number3:
   
   In this step we are not concerned with smallest, that will come soon.
3. Finally, you will need to find the smallest value by comparing the smallest to number3:
   
   Question: Will this last decision structure always work?

Test Plan

Even though you have coded a solution to the problem does not mean the solution is always going to work. Therefore, before executing the solution you need to create a test plan to outline all possible scenarios.

Scenario	Highest	Smallest	Y/N
number1 = 1 number2 = 2 number3 = 3	3	1
number1 = 2 number2 = 3 number3 = 1	3	1
number1 = 3 number2 = 1 number3 = 2	3	1
number1 = 3 number2 = 2 number3 = 3	3	2

Question: Are there other scenarios that can be tested?

Execute Solution

When you execute the solution, you will test all the scenarios of your Test Plan. The results are shown below:

From these results, return to your Test Plan:

Scenario	Highest	Smallest	Y/N
number1 = 1 number2 = 2 number3 = 3	3	1	Y
number1 = 2 number2 = 3 number3 = 1	3	1	Y
number1 = 3 number2 = 1 number3 = 2	3	1	Y
number1 = 3 number2 = 2 number3 = 3	3	2	Y

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