Lecture 2 Decision Making If-Else Statements Lecture Notes PDF

Structure Programming By Dr. Safa Elaskary Dr. Manar Elshazly Fall 2024-2025 1 2 Arithematic operation 3 Comparator operators 4 Lecture 2 : Decision Making: If-Else Statements 1. What i...

Structure Programming By Dr. Safa Elaskary Dr. Manar Elshazly Fall 2024-2025 1 2 Arithematic operation 3 Comparator operators 4 Lecture 2 : Decision Making: If-Else Statements 1. What is decision making? 2. Flowchart Symbols Overview 3. Python Conditional Statements 4. Flowchart vs. Code 5 1. What is Decision Making? ◦ Decision making in programming: ▪ Involves choosing different paths based on conditions. ◦ Conditional statements: ▪ Guide the flow of a program by allowing it to make decisions and execute specific blocks of code based on whether conditions are True or False. 6 2.Flowchart Symbols Overview Flowchart Symbols ◦ Oval: Represents the Start or End of the process. ◦ Diamond: Represents a decision point (e.g., True/False or Yes/ No). ◦ Rectangle: Represents actions or steps to be executed. ◦ Arrows: Indicate the flow direction from one step to another. 7 3.Python Conditional Statements Use if, else, and elif to manage decision-making in code. ◦ These statements evaluate specified conditions. ◦ Execute corresponding blocks of code based on whether the conditions are True or False. 8  Simple Flowchart Example ◦ This flowchart illustrates the decision process for determining if a person can ride a rollercoaster based on their height. ◦ Components: ◦ Start (Oval) ◦ Input Height (Rectangle) ◦ Decision: "Is height ≥ 120 cm?" (Diamond) ◦ Yes: "Allow to Ride" (Rectangle) → End (Oval) ◦ No: "Deny Access" (Rectangle) → End (Oval)  3.1. The if Statement Syntax in python: #code if condition: This code executes a block of code if the condition is True. 10  3.1. The if Statement Example: #code age = 18 if age >= 18: print("You are an adult.") This example checks if the variable age is greater than or equal to 18, and if so, it prints a message indicating that the person is an adult. 11  3.2. The else Statement Syntax in python: #code if condition: # code if condition is True else: # code if condition is False This code executes an alternative block of code if the condition is False. 12  3.2. The else Statement ◦ Example: #code age = 16 if age >= 18: print("You are an adult.") else: print("You are a minor.") In this example, if the variable age is less than 18, the program will print a message indicating that the person is a minor. 13  3.2. The else Statement ◦ Example: #code age = 16 if age >= 18: print("You are an adult.") else: print("You are a minor.") In this example, if the variable age is less than 18, the program will print a message indicating that the person is a minor. 14  3.3. The elif Statement ◦ Syntax in python: #code if condition: # code if condition is True elif condition: # code if this new condition is True else: # code if all previous conditions are False This code tests multiple conditions sequentially. 15  3.3. The elif Statement ◦ Example: #code grade = 85 if grade >= 90: print("Excellent") elif grade >= 75: print("Good") else: print("Needs Improvement") In this example, the program evaluates the grade and prints a corresponding message based on the defined conditions. 16 4.Flowchart vs. Code Flowchart to code Example : Check if a student's grade falls into different categories (Excellent, Good, Needs Improvement). 17 4.Flowchart vs. Code Flowchart to code Example : #code grade = 85 # Example input if grade >= 90: print("Excellent") elif grade >= 75: print("Good") else: print("Needs Improvement") 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Try to draw this flowchart Example : Number Comparison This example presents a flowchart and corresponding Python code for comparing two numbers to determine which is larger. 33 Try to convert 34 35