Lecture 2: Flowchart and Algorithm

Problem Solving

Problem-solving is the foundation of computer science.
A programmer must:

1. Understand how humans solve problems.
2. Translate this solution into a computer-executable algorithm.
3. Implement it using a specific programming language syntax.

Computers may solve problems differently than humans, emphasizing efficiency and logic.

Stages of Problem Solving

1. Analyze the problem.
2. Write algorithm steps using:
   • Pseudocode
   • Flowchart
3. Write the program in a programming language.
4. Translate the program into machine code.
5. Execute, test, and debug the program.
6. Document the software.

Algorithms

Definition

An algorithm is a set of rules and procedures used to solve a problem in a finite number of steps.
It consists of ordered, unambiguous instructions that describe a process and can be implemented in any programming language.

Characteristics of a Good Algorithm

1. Each step must be clear and unambiguous.
2. The algorithm must terminate after a finite number of steps.
3. The process must lead to the correct solution.
4. Steps must be written in precise language.

Algorithm Design Techniques

Algorithms can be expressed using:

1. Flowcharts

A graphical representation that shows the logical sequence of operations and their relationships.

2. Pseudocode

A textual representation that uses English-like statements to describe program logic.

Pseudocode

Definition

Pseudocode is a simplified, language-like representation of algorithmic logic written using commands that resemble real programming languages.

It focuses on problem-solving logic rather than language syntax and can be easily converted into actual code.

Components

• Keywords
• Sections
• Statements

Structure Types

1. Sequential Statements: Executed one after another.
2. Decision Statements: Use if-else or switch-case for conditional execution.
3. Looping Statements: Use for, while, or do-while for repetition until a condition is met.

Flowcharts

Definition

A flowchart is a graphical representation showing the sequence of steps in a process or program, using standardized symbols.
It is one of the most effective tools for analyzing and visualizing systems.

Importance and Uses of Flowcharts

1. Simplify Understanding

   • Show logical flow of processes visually.
   • Easy for programmers and non-programmers to grasp.

2. Assist in System Analysis

   • Identify the relationship between input, process, and output.
   • Detect errors or inefficiencies early.

3. Aid in Program Development

   • Each flowchart step can be directly translated into code (e.g., in C++).
   • Minimizes logical errors before implementation.

4. Documentation and Maintenance

   • Acts as a reference document for future updates and debugging.

5. Enhance Communication

   • Provides a common visual language between developers and analysts.

6. Detect Logic Errors Early

   • Logic can be tested visually before coding.

Common Flowchart Symbols

Symbol	Shape	Description
Terminator	Oval	Represents the Start or End of the process.
Flow Line	Arrow	Shows the direction of control flow.
Process	Rectangle	Denotes an operation or calculation.
Decision	Diamond	Represents a conditional check (Yes/No or True/False).
Input/Output	Parallelogram	Indicates data input or output operations.
Connector	Circle	Connects different parts of a flowchart.
Loop Symbol	Hexagon	Represents a loop structure (e.g., for-loop).
Text Label	—	Describes the function or operation in the shape.

Flowchart Design Guidelines

• The flowchart must be neat, complete, easy to follow, and unambiguous.
• Flow direction should be left-to-right and top-to-bottom.
• Start symbol: one outgoing flow line only.
• End symbol: one incoming flow line only.
• Process symbol: one outgoing flow line.
• Decision symbol: one incoming and two outgoing flow lines.
• Use annotations to clarify logic when needed.

Key Qualities of a Good Flowchart

1. Neat: Well-organized with no unnecessary line crossings.
2. Complete: Includes all essential steps from start to finish.
3. Easy to Follow: Logical and clearly directed flow.
4. Unambiguous: Each symbol and statement must have a single, clear meaning.

A good flowchart should be clear, logical, and universally understandable.

Advantages of Flowcharts

• Simplify communication and understanding.
• Allow for effective problem analysis.
• Serve as proper documentation tools.
• Help write programs more efficiently.
• Facilitate error detection and program correction.

Disadvantages of Flowcharts

• Can become complex for large problems.
• Modifications often require redrawing the entire flowchart.
• Manual reproduction of flowcharts can be cumbersome.
• Excessive details may distract from the main logic.

Summary

• Algorithms provide structured solutions to problems.
• Pseudocode expresses logic in human-readable form.
• Flowcharts visualize processes using standardized symbols.
• Good flowcharts and pseudocode make programming more reliable, maintainable, and efficient.