Question

How does a dual alternative decision structure work?

Short answer

Answer: A dual alternative decision structure is a programming concept where the program chooses between two possible actions based on the evaluation of a specific condition, typically using "if-else" statements. To illustrate this, let's consider an example where we check if a person's age is greater than or equal to 18. In Python, a dual alternative decision structure would look like: ```python if age >= 18: print("You are an adult.") else: print("You are not an adult.") ``` Here, the program first evaluates the condition (age >= 18). If the condition is True, the code inside the "if" block is executed, displaying "You are an adult.". If the condition is False, the code inside the "else" block is executed, displaying "You are not an adult.".

Step-by-step solution

Understand the Basics of a Dual Alternative Decision Structure

A dual alternative decision structure is used in programming when the program has two possible actions or outcomes based on a specific condition being met or unmet. Typically, there are two blocks of code in this structure, where only one block will be executed depending on the result of the condition. The most common example in programming languages is the use of "if-else" statements.

Understand the Components of the "if-else" Statement

The "if-else" statement consists of three major components: 1. "if" keyword: It is used to check if a specified condition is True or False. 2. Condition: A boolean expression that evaluates to either True or False. 3. "else" keyword: It denotes the alternative action if the condition is False.

Define the Condition

In this step, you need to define the condition that will determine whether the program will execute the first block of code or the alternative block of code. For this example, let's use the condition of checking if the age of a person is greater than or equal to 18.

Write the "if" Block of Code

Next, you need to write the code that will be executed if the condition is True. In our example, if the age is greater than or equal to 18, we will display a message "You are an adult.". In Python, this looks like: ```python if age >= 18: print("You are an adult.") ```

Write the "else" Block of Code

Now, write the code that will be executed if the condition is False. In our example, if the age is less than 18, we will display a message "You are not an adult.". In Python, this looks like: ```python else: print("You are not an adult.") ```

Combine the "if" and "else" Blocks

Finally, put the "if" and "else" blocks together to create the complete dual alternative decision structure. In Python, the final structure should look like this: ```python if age >= 18: print("You are an adult.") else: print("You are not an adult.") ``` Now you know how a dual alternative decision structure works. When the program executes, it will first evaluate the condition (age >= 18). If the condition is True, the code inside the "if" block will be executed, and if the condition is False, the code inside the "else" block will be executed.