Flowcharts for Algorithms

Overview

This lecture introduces flowcharts as visual tools for representing algorithms using standardized symbols, covers their main components, and provides step-by-step examples for basic programming problems.

Introduction to Flowcharts

• A flowchart visually represents the sequence, decisions, and processes in algorithms using standard symbols.
• Flowcharts are helpful in planning and designing programs before actual coding.

Flowchart Symbols and Their Functions

• Terminator (Ellipse): Indicates the start and end of a flowchart.
• Preparation (Parallelogram or Rectangle): Used to declare or assign values to variables or constants.
• Input/Output (Parallelogram): Represents data input from or output to the user.
• Decision (Diamond): Used for branching (if-else conditions).
• Process (Rectangle): Indicates operations such as assignments or calculations.
• Flow lines (Arrows): Show the direction of flow from one step to another.
• Connector (Circle): Connects flowcharts across separate pages or areas.

Example 1: Display "Hello World"

• Start with a terminator labeled "Start."
• Use an output symbol to display "Hello World."
• End with a terminator labeled "End."

Example 2: Display Name and Age

• Start, then output name and age on separate lines.
• Alternatively, use preparation to declare variables for name and age, and output each variable.
• Demonstrates the use of string and integer variables.

Example 3: Check for Minor or Legal Age

• Start, prompt for user's age as input.
• Use a decision symbol to check if age ≤ 17.
• Output "You are a minor" if true; else output "Legal."
• Finish with terminator.

Example 4: Sum of Two Numbers

• Start the flowchart.
• Input first and second numbers from user.
• Use a process symbol to calculate their sum: sum = first + second number.
• Output the value of sum.
• End the flowchart.

Key Terms & Definitions

• Flowchart — A diagram that depicts the sequence of operations in a process or program.
• Terminator — Symbol used to indicate the start and end points of a flowchart.
• Preparation — Step where variables or constants are initialized or assigned.
• Input/Output — Steps where data is received from or displayed to the user.
• Decision — Symbol representing branching logic (e.g., if-else).
• Process — Step showing operations like calculations or assignments.
• Connector — Used to join flow lines across different pages.

Action Items / Next Steps

• Practice drawing flowcharts for common programming problems using the symbols discussed.
• Prepare questions or clarifications for the next live online discussion.
• Export flowchart examples as PNG images for submission if required.