Nested Conditionals Chapter Notes | AP Computer Science Principles - Grade 9 PDF Download

Introduction

Nested conditionals are an important concept in AP Computer Science Principles, allowing programs to handle more complex decision-making. This chapter explains how to place one conditional statement inside another, known as nested conditionals. By using nested if statements, programmers can check multiple conditions in a specific order to control the flow of a program. Understanding nested conditionals helps create programs that can evaluate several requirements before taking action.

Nested Conditionals

Nested conditional statements involve placing one conditional statement within another. This structure enables programs to handle complex decision-making by checking multiple conditions in a hierarchical manner.

Example of Nested Conditionals

• Example in Python:
  • Variables: strawberries_in_fridge = 7, number_of_eggs = 12.
  • Code checks if strawberries_in_fridge >= 7:
    • If true, it prints: "You can make strawberry shortcake!"
    • Then, it checks a nested condition: if number_of_eggs < 12:
      • If true, it prints: "... if you go to the store first."
    • Otherwise (else), it prints: "So start baking!"
  • Output for this case: "You can make strawberry shortcake! So start baking!" because strawberries_in_fridge >= 7 is true and number_of_eggs < 12 is false.
• The outer condition (strawberries_in_fridge >= 7) must be true for the nested condition (number_of_eggs < 12) to be checked.
• If strawberries_in_fridge < 7, none of the code inside the outer if statement, including the nested if, would run.
• The program always checks the strawberry condition first, and only evaluates the egg condition if there are enough strawberries.

Important Notes

• Nested if statements are part of the outer if block, so proper indentation is critical to ensure correct execution.
• The structure allows for layered decision-making, but over-nesting can make code harder to read, so use it judiciously.

Key Term

• Nested Conditional Statements: A programming technique where one conditional statement is placed inside another, enabling the evaluation of multiple conditions for more intricate program logic.