Perak Digital Transformation Centre

Chapter 2: Algorithms, Pseudocode and Flowcharts

Learn how to plan a program before writing Python code using step-by-step algorithms, beginner-friendly pseudocode, and professional flowchart diagrams.

Problem Solving Program Logic Flowchart Design
START
↓
Input Marks
↓
Marks ≥ 50?
PASS / FAIL

2.1 Chapter Overview

Before writing a Python program, a programmer must understand the problem clearly and design a solution. Algorithms, pseudocode and flowcharts help students plan the logic of a program before coding.

This chapter teaches learners how to think like programmers. Instead of directly typing code, students will learn how to break a problem into smaller steps, arrange those steps logically, and represent the solution using written instructions and visual diagrams.

Key Idea: Good coding starts before the keyboard. A good programmer first understands the problem, plans the logic, checks the flow, and only then writes the program.

2.2 Chapter Objectives

  • Understand the meaning and purpose of algorithms.
  • Write simple algorithms for beginner programming problems.
  • Understand the structure and purpose of pseudocode.
  • Create pseudocode using clear, human-readable instructions.
  • Identify common flowchart symbols and their functions.
  • Design flowcharts for simple programming problems.
  • Convert algorithm logic into Python code.

Learning Outcomes

  • Explain how algorithms support programming logic.
  • Differentiate between algorithm, pseudocode and flowchart.
  • Draw simple flowcharts using correct symbols.
  • Create step-by-step logic for Python programs.

2.3 What is an Algorithm?

An algorithm is a step-by-step set of instructions used to solve a problem or complete a task. In programming, an algorithm explains what the program should do before the actual code is written.

Real-Life Example: Making Tea

  1. Start.
  2. Boil water.
  3. Add tea powder or tea bag.
  4. Add sugar and milk if required.
  5. Stir the tea.
  6. Serve the tea.
  7. End.
Programming Connection: Just like making tea requires steps, a computer program also requires clear instructions in the correct order.

2.4 Characteristics of a Good Algorithm

Clear

Each step must be easy to understand and not confusing.

Ordered

Steps must be arranged in the correct sequence.

Finite

The algorithm must have a clear ending point.

Effective

Each step must contribute towards solving the problem.

2.5 Algorithm Development Process

Programmers commonly follow a structured process when creating algorithms.

1Understand Problem
2Identify Inputs
3Plan Processing
4Define Output
5Test Logic

2.6 Input, Process and Output Model

Most beginner programs follow the Input-Process-Output model.

Component Meaning Example
Input Data entered into the program. Student marks
Process Calculation or decision performed by the program. Check whether marks are greater than or equal to 50
Output Final result displayed by the program. Pass or Fail
INPUT → PROCESS → OUTPUT

2.7 What is Pseudocode?

Pseudocode is a simple way of writing program logic using English-like instructions. It is not a real programming language, so it does not follow strict Python syntax.

Pseudocode helps learners focus on logic before worrying about exact coding rules.

Example: Check Student Result

START
INPUT marks
IF marks >= 50 THEN
    DISPLAY "Pass"
ELSE
    DISPLAY "Fail"
END IF
END

2.8 Why Pseudocode is Important

  • It helps students plan the program before coding.
  • It is easier to understand than actual programming syntax.
  • It allows programmers to discuss logic with others.
  • It reduces mistakes during coding.
  • It can be converted into Python, Java, C++ or other programming languages.
Beginner Tip: If you cannot explain your program in pseudocode, you may not yet fully understand the problem.

2.9 Common Pseudocode Keywords

Keyword Purpose Example
START Beginning of the logic. START
INPUT Accept data from user. INPUT name
PROCESS Perform calculation or action. total = marks1 + marks2
IF / ELSE Make decision. IF age >= 18 THEN
DISPLAY Show output. DISPLAY total
END End of the logic. END

2.10 What is a Flowchart?

A flowchart is a visual diagram that shows the steps of a program using symbols and arrows. It helps programmers see the flow of logic clearly.

Flowcharts are especially useful for beginners because they make abstract programming logic easier to understand visually.

START
↓
INPUT DATA
↓
PROCESS
↓
DISPLAY OUTPUT
↓
END

2.11 Common Flowchart Symbols

Symbol Name Purpose
Oval Start / End Shows where the process begins or ends.
Parallelogram Input / Output Shows data input or output display.
Rectangle Process Shows calculation or processing step.
Diamond Decision Shows a condition such as Yes / No or True / False.
Arrow Flow Line Shows the direction of program flow.

2.12 Worked Example 1: Add Two Numbers

Problem

Create logic to input two numbers, add them, and display the total.

Algorithm

  1. Start.
  2. Input first number.
  3. Input second number.
  4. Add both numbers.
  5. Display total.
  6. End.

Pseudocode

START
INPUT number1
INPUT number2
total = number1 + number2
DISPLAY total
END

Python Code

number1 = 10
number2 = 5

total = number1 + number2

print("Total:", total)
Output:
Total: 15

2.13 Worked Example 2: Check Pass or Fail

Problem

A student passes if marks are 50 or above. Otherwise, the student fails.

Algorithm

  1. Start.
  2. Input student marks.
  3. If marks are greater than or equal to 50, display Pass.
  4. Otherwise, display Fail.
  5. End.

Pseudocode

START
INPUT marks
IF marks >= 50 THEN
    DISPLAY "Pass"
ELSE
    DISPLAY "Fail"
END IF
END

Python Code

marks = 75

if marks >= 50:
    print("Pass")
else:
    print("Fail")
Output:
Pass

2.14 Worked Example 3: Find the Largest Number

Problem

Compare two numbers and display the larger number.

Pseudocode

START
INPUT number1
INPUT number2
IF number1 > number2 THEN
    DISPLAY number1
ELSE
    DISPLAY number2
END IF
END

Python Code

number1 = 25
number2 = 40

if number1 > number2:
    print("Largest Number:", number1)
else:
    print("Largest Number:", number2)
Output:
Largest Number: 40

2.15 Flowchart Logic for Pass or Fail

The following text-based flowchart shows how a Pass or Fail decision works.

START
↓
INPUT MARKS
↓
MARKS ≥ 50?
↙ YES           NO ↘
DISPLAY PASS DISPLAY FAIL
↓
END

2.16 Difference Between Algorithm, Pseudocode and Flowchart

Item Format Main Purpose
Algorithm Step-by-step instructions Explains the solution clearly.
Pseudocode English-like programming logic Prepares logic before coding.
Flowchart Visual diagram using symbols Shows program flow visually.

2.17 Common Beginner Mistakes

Mistake Problem Correction
Skipping planning Students start coding without understanding the logic. Write algorithm first.
Unclear steps Instructions are too general or confusing. Write simple and specific steps.
Wrong flowchart symbols Decision and process symbols are mixed up. Use diamond for decision and rectangle for process.
No ending point The logic does not clearly stop. Always include END.

2.18 Hands-On Practice

Activity 1: Simple Greeting Algorithm

Write an algorithm and pseudocode to input a student name and display a welcome message.

Activity 2: Area of Rectangle

Create an algorithm, pseudocode and Python code to calculate the area of a rectangle.

length = 10
width = 5

area = length * width

print("Area:", area)

Activity 3: Odd or Even Number

Design pseudocode and a flowchart to check whether a number is odd or even.

Mini Project: Student Grade Decision

Create an algorithm, pseudocode, flowchart and Python code for a student grading system. The program should input marks and display Grade A, B, C or Fail.

2.19 Assessment Quiz

Answer the following questions. Correct Answer = +1 Mark Wrong Answer = -0.5 Mark

1. An algorithm is a step-by-step set of instructions used to solve a problem.

2. Pseudocode must follow exact Python syntax.

3. A diamond symbol is normally used for decision making in a flowchart.

4. Flowcharts use arrows to show the direction of program flow.

5. The Input-Process-Output model is useful for planning beginner programs.

Your Score: 0

Practical Assessment Task

Create an algorithm, pseudocode and flowchart for a program that calculates total marks and average marks for three subjects. Then write the equivalent Python code.

2.20 Chapter Summary

In this chapter, learners studied algorithms, pseudocode and flowcharts. Algorithms explain the solution in steps, pseudocode expresses logic in English-like programming form, and flowcharts visually show how a program flows from start to end.

Remember: Programming is not only typing code. It is a process of thinking, planning, designing, testing and improving solutions.