CS50 Lecture Notes - Introduction to Computer Science

Lecturer: David Malan

Introduction

• Course: Harvard University's Introduction to Computer Science and the Art of Programming
• Personal Story:
  • Initially hesitant to take CS50 due to lack of comfort with computers.
  • Eventually inspired by a class with Brian Kernighan and found a passion for computer science.
  • Encourages students from all backgrounds.

Importance of Computer Science

• Applicability:
  • Relevant to arts, humanities, social sciences, natural sciences, etc.
  • Teaches problem-solving and practical programming skills.
• Challenge and Reward:
  • Initial difficulty akin to drinking from a fire hose.
  • Returns on investment higher once the challenge is met.
• Goal:
  • Equip students to self-teach new technologies beyond the course.
  • Focus on personal progress rather than competing with classmates.

Course Structure

• Support:
  • Teaching fellows, assistants, and community events.
• Events:
  • CS50 Puzzle Day: Social event with logic puzzles.
  • CS50 Hackathon: Intensive overnight coding event.
  • CS50 Fair: Showcase of student projects.

Computer Science Fundamentals

• Definition: Study of information representation and processing.
• Core Concept: Computational thinking applied to solve problems.
• Problem Solving:
  • Input -> Process -> Output model.
  • Example: Problem-solving via algorithms.

Algorithms

• Definition: Step-by-step instructions for solving problems.
• Efficiency: Illustrated using phone book search (linear vs. binary search).
• Complexity:
  • Linear search: O(n)
  • Binary search: O(log n)

Binary Representation

• Basics: Computers use binary (0s and 1s) due to transistor states.
• Counting: Binary digits (bits) represent numbers.
• Text Representation:
  • ASCII for letters (e.g., 'A' is 65).
  • Unicode for global character support.

Media Representation

• Colors: RGB model using 3 bytes per pixel.
• Images and Videos: Sequence of pixels; videos as motion pictures.
• Sound: Represented using frequency, volume, duration.

Programming Concepts

• Languages: Start with C, move to higher-level languages like Python.
• Scratch Programming:
  • Visual language using blocks.
  • Introduction to concepts like loops, conditionals, and functions.
  • Demonstrated using visual programs (e.g., cat meowing, Oscar the Grouch game).

Artificial Intelligence (AI)

• AI Basics: Use of large language models and neural networks.
• Chatbot Example: Simple conditionals vs. AI-based learning.
• Tools: CS50-specific AI tools for educational use.

Conclusion

• CS50 is an introduction to the broader world of computing and programming.
• The course combines theoretical knowledge with practical experience.
• Students are encouraged to explore and innovate with the skills learned.