CS50 Lecture Notes

Introduction to Computer Science & Programming

• Instructor: David J. Malan
• Course: CS50, Harvard University's Introduction to Computer Science
• Special Guest: Spot the Robot, Boston Dynamics (Demo)

Instructor's Background

• David Malan took CS50 as a sophomore after initially gravitating towards Government studies.
• Found programming fun and switched to a letter grade after enrolling pass/fail.
• Emphasizes that computer science is a general-purpose way of solving problems applicable to many fields.
• Encourages students to get comfortable feeling uncomfortable with new material.

Course Overview

• Languages learned:

  • C: Foundational, older language.
  • Python: Modern, used for data science, web apps.
  • SQL: For databases.
  • JavaScript, HTML, CSS: For web development.

• Course Structure:

  • Weekly problem sets (assignments).
  • Sections/recitations for different comfort levels.
  • Final project representing a capstone of CS50 experience.

Key Concepts

• Problem Solving: Focus on how to solve problems using algorithms and computational thinking.
• Learning Objectives for Today:
  • Representing numbers, letters, colors, images, videos, and audios.
  • Writing algorithms and implementing them with code.
• Binary System:
  • Binary (base-2) representation.
  • Bits and bytes (8 bits = 1 byte).
• Text Representation:
  • ASCII and Unicode for character representation.
  • Hexadecimal (base-16) notation for compact representation.
• Color Representation:
  • RGB model (Red, Green, Blue) using bytes (0-255).
• Algorithm Efficiency:
  • Binary search as a model for efficient problem solving.

Course Activities & Community

• CS50 Lunches: Weekly at Changsho restaurant.
• CS50 Puzzle Day: Team-based problem-solving with puzzles, pizza, and prizes.
• CS50 Hackathon: Intense programming night ending with IHOP pancakes.
• CS50 Fair: Exhibition of final projects.
• CS50 Culture: Focus on personal growth vs. peer comparison.

Artificial Intelligence (AI) in CS50

• AI-based tools like the CS50 Duck to help students.
• Restricted use of AI-based tools for assignments, with CS50's AI tools permitted.
• Introduction of large language models (LLMs) like ChatGPT.

Introduction to Scratch Programming

• Purpose: Visual programming to understand basic concepts before C.
• Interface: Blocks representing actions, controls, and events.
• Basics: Hello World Example
  • Using "events" and "looks" blocks to make the cat say hello.
• Advanced Scratch Programs:
  • Custom functions (meow example), loops, conditionals, and games.
• Examples:
  • Oscar Time Game: Trash falling into Oscar the Grouch’s bin.
  • Interactive games using video sensing and keyboard input.

Conclusion

• Encouragement to take incremental steps in problem-solving.
• Final note: Cake served in the Transept and meet Spot the robot.