CS50's Introduction to Computer Science
Harvard's flagship introduction to programming and computer science, taught by David Malan, starts with the language C and moves through arrays, algorithms, memory, and data structures before pivoting to Python, SQL, and HTML, CSS, and JavaScript. Eleven weeks of lecture videos pair with problem sets, shorts, and a final project that culminates the course, and roughly two thirds of students who take it at Harvard have never studied computer science before. You work through Scratch in week 0, C for the low-level fundamentals, then Python and SQL, and a week on cybersecurity closes things out. Submitting problem sets and the final project through an edX account earns feedback, and a paid verified certificate is optional. Graduates leave able to write, debug, and reason about programs across several languages.