CS50x 2026 - Lecture 0 - Scratch

David Malan introduces computer science as the study of information representation and processing, emphasizing problem-solving through computational thinking. He explains how computers use binary code (zeros and ones) to represent various forms of data, including numbers, letters, images, and sound, detailing the ASCII and Unicode standards for character encoding and the RGB system for color representation. Malan illustrates algorithms with the example of searching for a contact in a phone book, comparing linear and logarithmic search efficiencies. He also explores Scratch, a visual programming language, demonstrating how to create interactive programs using functions, loops, and conditionals, and builds a simple chatbot using Python and OpenAI.