30 min
📘 Computer Science — Unit 2 Notes
1. Computer

A computer is a machine used to solve problems by accepting inputs, performing operations, and producing outputs. It performs operations according to algorithms/programs written by humans.

2. Problem

A problem is a challenge or situation that needs to be overcome using appropriate actions.

3. Computing Problem

A computing problem is a problem that can be solved step-by-step using computation, involving arithmetic and/or logical operations.

A computing problem has:

Well-defined input
A desired output satisfying specific requirements
4. Types of Computing Problems
Decision Problem

A problem whose answer is a binary response, such as:

Yes / No
True / False
1 / 0

Example: Is 97 an even number? → No.

Search Problem

A problem in which we find a particular item or solution that satisfies given conditions.

Counting Problem

A problem in which we determine the number of possible arrangements, combinations, or solutions.

Example: 2 pants × 5 shirts = 10 possible outfits.

5. Problem Solving
Simple Problem
Identify the core problem.
Design a plan.
Implement the plan.
Evaluate the result.

Remember: I → P → I → E

Complex Problem
Identify the core problem.
Decompose it into smaller sub-problems.
Identify potential plans for each sub-problem.
Select and design the best plan.
Implement the plan.
Evaluate the result.

Remember: I → D → P → S → I → E

6. IPO Model

IPO = Input → Processing → Output

Input

The requirements/data provided to the computer system.

Processing

The operations or computations performed on the input.

Output

The result presented after processing.

IPO Chart

An IPO chart is a tabular tool used to visually represent the Input, Processing, and Output of a problem.

7. Computational Thinking

Definition:
Computational thinking is a way of thinking that enables us to use computation to solve problems.

Importance

It helps us develop repeatable solutions that can solve not just one problem instance but similar instances of the problem.

Properties of Computational Thinking
1. Decomposition

Breaking a large problem into smaller, manageable sub-problems.

2. Abstraction

Removing unnecessary details and focusing on the essential information needed to solve the problem.

3. Pattern Recognition

Examining a problem to identify patterns or similarities with previously solved problems.

4. Algorithmic Thinking

Designing a step-by-step solution to a problem.

8. Logical Thinking

Logical thinking means analyzing a situation using reasoning and relevant facts and making sensible decisions accordingly.

📌 Important: Logical thinking is a part of computational thinking.

Computers can apply logic according to their programming, but they don't independently reason like humans.

9. Algorithmic Thinking

Algorithmic thinking is a problem-solving approach for developing a step-by-step solution.

Algorithms can be represented using:

Flowchart

A diagrammatic representation of an algorithm showing the sequence of operations required to solve a problem.

Importance of Flowcharts
Show the sequence of operations.
Make the solution easier to understand.
Help analyze problems.
Help programmers plan before writing code.
🔥 Flowchart Symbols
Shape	Meaning
Oval	Start / Stop
Parallelogram	Input / Output
Rectangle	Process
Diamond	Decision

OVAL → START/STOP
PARALLELOGRAM → INPUT/OUTPUT
RECTANGLE → PROCESS
DIAMOND → DECISION

10. Concept Map

A concept map is a graphical tool that represents concepts and the relationships between them.

Concepts → boxes/circles
Relationships → lines/arrows
Connections → linking words/phrases
🧠 ULTRA-QUICK REVISION

Computing problem: Step-by-step computation.

3 problem types:
➡️ Decision = Yes/No
➡️ Search = Find
➡️ Counting = How many?

Simple problem:
➡️ Identify → Plan → Implement → Evaluate

Complex problem:
➡️ Identify → Decompose → Plans → Select → Implement → Evaluate

IPO:
➡️ Input → Processing → Output

Computational thinking:
➡️ Decomposition → Abstraction → Pattern Recognition → Algorithm Design

Flowchart:
➡️ Oval = Start/Stop
➡️ Parallelogram = I/O
➡️ Rectangle = Process
➡️ Diamond = Decision

Concept map:
➡️ Concepts + relationships