J277 OCR GCSE Computer Science - Paper 2: Computational Thinking, Algorithms, and Programming

This document captures key details from the lecture on computational thinking, algorithms, and programming as per the J277 OCR GCSE specification for paper 2.

Computational Thinking Principles

1. Abstraction

   • Simplifying complex problems by focusing on essential details.
   • Examples: Inbuilt functions like sort and rand.
   • Exam scenarios may involve identifying how abstraction is applied.

2. Decomposition

   • Breaking down complex problems into manageable sub-problems.
   • Allows for easier understanding, debugging, and concurrent development.
   • Example: Video games design process.

3. Algorithmic Thinking

   • Designing step-by-step solutions or instructions to solve problems.
   • Methods: Pseudo code, flowcharts, programming languages like Python/Java.
   • Exam tasks may include identifying inputs, processes, and outputs.

Algorithms

Writing Algorithms

• Pseudo code: Informal, code-like instructions.
• Flowcharts: Visual step representation using specific shapes.
• High-level programming: Translate algorithms to code like Python or Java.

Searching Algorithms

• Linear Search
  • Checks each item sequentially.
  • Suitable for small or unsorted data sets.
• Binary Search
  • Prerequisite: Data must be sorted.
  • Efficiently divides data set to search.

Sorting Algorithms

• Bubble Sort
  • Compares and swaps adjacent values.
  • Simple but inefficient for large data sets.
• Insertion Sort
  • Efficient for small data sets, sorts by shifting unsorted values.
• Merge Sort
  • Divide and conquer method, efficient for large data sets.

Programming Constructs

Basic Constructs

• Sequence: Ordered execution of instructions.
• Selection: Making decisions using if, else, switch/match.
• Iteration: Repeating code using loops (for, while, do until).

Data Types and Structures

• Data Types: Character, String, Integer, Real/Float, Boolean.
• Arrays: 1D and 2D arrays for storing data sets.

Subprograms

• Procedures: Perform tasks without returning values.
• Functions: Return values for further use.
• Parameters and Variables: Local, global, passing values.

Random Numbers

• Generated using functions like rand int, inclusive range.

Databases

SQL (Structured Query Language)

• Manipulate data with commands like SELECT, FROM, WHERE.
• Example queries and understanding syntax for GCSE exams.

Defensive Design

Techniques

• Authentication: Secure access via passwords, biometrics.
• Input Sanitization and Validation: Remove invalid data, ensure correct format.

Validation Checks

• Range, Type, Length, Format, Presence, Lookup Checks.

Testing

Types of Testing

• Iterative Testing: Conducted during development.
• Final Testing: After development completion.

Errors

• Syntax Errors: Violate language grammar, detected by compilers.
• Logic Errors: Correct syntax but incorrect outcomes.

Test Data

• Normal, Boundary, Invalid, Erroneous Data.

Logic Gates and Boolean Logic

Boolean Operators

• NOT, AND, OR: Combining, comparing logic conditions.
• Truth tables and logic gate representations.

High-Level vs. Low-Level Languages

High-Level Languages

• Close to human language, easier to read, write, and maintain.

Low-Level Languages

• Machine code, faster execution, hardware-specific.

Translators

• Interpreters: Line-by-line execution.
• Compilers: Translates entire code to machine language.

Integrated Development Environment (IDE)

Tools

• Editors: Code entry and editing.
• Error Diagnostics: Debugging tools.
• Runtime Environment: Code execution, error reporting.
• Translators: High-level to machine code conversion.

Additional Tools

• Breakpoints, variable watches for debugging.

These notes cover essential concepts and methods covered in the OCR GCSE Computer Science Paper 2 lecture. Ensure to review algorithms, programming constructs, data handling, and defensive design principles thoroughly for exam preparation.