COMP121L_Decision_Making

Lesson Overview

• Institution: Manuel S. Enverga University Foundation, Lucena City

• Course: Computer Fundamentals and Programming 2

• Instructor: Hannah Shimara P. Santonil

• Focus: Decision structures and Boolean logic in Python programming

Learning Outcomes

• Understand the basic concepts of Python programming language

• Learn about:

  • The if statement

  • The if-else statement

  • Comparing strings

  • Nested decision structures and the if-elif-else statement

  • Logical operators

  • Boolean operators

Introduction to Decision Structures

• Definition: Decision structures allow a program to execute actions based on specific conditions.

• Types of decisions:

  • If statement: Single alternative

  • If-else statement: Dual alternative

  • Case structure: Multiple alternative decisions

The if Statement

• Concept: Creates a decision structure allowing multiple execution paths based on Boolean expression truth.

• A set of statements executes when a specified condition is true.

Control Structures

• Control Structure: Logical design dictating the execution order of statements.

• Sequence Structure: Executes statements in the order written.

• Decision (Selection) Structure: Executes statements based on the existence of specific conditions.

Representation

• The diamond symbol represents a true/false condition in decision structures.

• Single Alternative Structure: Only one path of execution based on condition.

Python Syntax

• Syntax Example: In Python, written as:

  if condition:
      statement
      statement

Boolean Expressions and Relational Operators

• Relational Operator: Determines specific relationships between two values.

Example of if Statement

• Scenario: A program to average three test scores and congratulate the user if above 95.

• Pseudocode:

  • Input: Three test scores

  • Process: Calculate average

  • Output: Display average, congratulatory message if > 95

Sample Program

• Program: test_average.py

• Inputs:

  • Test 1 score (e.g., 82)

  • Test 2 score (e.g., 76)

  • Test 3 score (e.g., 91)

• Displays average and congratulates if average ≥ 95.

The if-else Statement

• Concept: Executes one block if the condition is true, another if false.

• Provides two execution paths based on the condition.

Syntax Example

• Python:

  if condition:
      statements
  else:
      statements

Example: Payroll Program

• Scenario: Calculate gross pay with overtime.

• Conditions:

  • If hours > 40, compute overtime.

  • Include a pay rate in calculation.

Comparing Strings

• Concept: Test string values to create decision structures.

• Example Program: Compare input password to a predefined correct password.

Nested Decision Structures and if-elif-else Statement

• Concept: Tests multiple conditions with nested structures.

• Syntax:

  if condition_1:
      statements
  elif condition_2:
      statements
  else:
      statements

• Especially useful for grading or range scenarios.

Logical Operators

• Concept: Used to connect multiple Boolean expressions.

• Types:

  • and: True if both conditions are true.

  • or: True if at least one condition is true.

  • not: Reverses the truth of a Boolean expression.

Sample Use Cases

• Example: Check if values fall within a range using and and or operators.

Boolean Variables

• Concept: Can represent values True or False, often used as flags for conditions.

• Usage Example:

  if sales_quota_met == True:
      print('You have met your sales quota!')

Conclusion

• Boolean logic and decision structures form the fundamental basis for control flow in programming, enabling conditional execution and logical reasoning in code.