Question

How does a dual alternative decision structure work?

Short answer

Question: Explain a dual alternative decision structure and provide a simple example in Python. Answer: A dual alternative decision structure, also known as an 'if-else' statement, is a programming concept that performs one action if a certain condition is met and another action if it is not. It involves using 'if' and 'else' statements, and evaluates a condition that results in either True or False. For instance, let's consider a program that determines if a student passes or fails an exam based on their score. The passing score is 50. So, the condition we check is whether the student's score is greater than or equal to 50. In Python, this can be represented as: ```python if score >= 50: print("You passed!") else: print("You failed.") ``` Here, if the student's score is greater than or equal to 50 (True), the program will print "You passed!". If the student's score is less than 50 (False), it will print "You failed.". The dual alternative decision structure allows for more complex and dynamic behavior in programming by enabling decisions based on specific conditions.

Step-by-step solution

Understanding Conditional Statements

Conditional statements are an essential part of programming, as they allow the program to make decisions based on specific conditions being True or False. This involves the use of 'if' and 'else' statements, and the logic behind them.

The Basic Structure of a Dual Alternative Decision Structure

A dual alternative decision structure, also known as an 'if-else' statement, is a way to perform one action if a certain condition is met, and another action if it is not. The syntax for a dual alternative decision structure is as follows: ``` if condition: action 1 else: action 2 ``` Here, 'condition' is an expression that evaluates to either True or False. If the condition is True, 'action 1' is executed; if the condition is False, 'action 2' is executed.

Example Scenario

Let's consider an example to better understand how a dual alternative decision structure works. We will use a simple program that determines whether a student passes or fails an exam based on their score.

Define the Condition

For this example, let's say that the passing score for the exam is 50. Therefore, the condition we are checking is whether the student's score is greater than or equal to 50. In Python, the condition can be represented as follows: ```python score >= 50 ```

Define the Actions

Now that we have our condition, we need to define the actions to take based on whether the condition is True or False. 1. If the condition is True (the student's score is greater than or equal to 50), the action will be to print "You passed!" 2. If the condition is False (the student's score is less than 50), the action will be to print "You failed."

Create the Dual Alternative Decision Structure

Now let's put everything together to create the dual alternative decision structure for our example: ```python if score >= 50: print("You passed!") else: print("You failed.") ``` With this structure, the program will evaluate the condition (score >= 50) and execute the appropriate action based on whether the condition is True or False. In conclusion, a dual alternative decision structure works by evaluating a condition and executing one of two possible actions based on the result of the evaluation. It provides a simple way to make decisions in programming, allowing for more complex and dynamic behavior.