Harvard study guides, course by course
Harvard College courses run the range from gentle gen-eds to legendary gauntlets like Math 55, with grades driven by problem sets and exams rather than attendance. Because courses like CS50 (via edX as CS50x) and Stat 110 (free lectures online) have global audiences, many students studying these syllabi are self-learners working through the public materials rather than enrolled undergraduates — the study challenges are the same either way.
Harvard courses pair a department name with a number — CS50, Stat 110, Math 55 — with letter suffixes for semester halves (EC 10A/10B, Math 21A/21B). Several famous courses, most notably CS50, are also published free online, so these codes get searched by far more people than ever enroll at Harvard.
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CS50 — Introduction to Computer Science
CS50 is Harvard's famous intro to computer science, taught by David Malan — and through CS50x on edX, almost certainly the most-taken and most-searched college course in the world. It moves from C through data structures, memory, and algorithms to Python, SQL, and web development, ending with a final project.
CS 51 — Abstraction and Design in Computation
CS 51 is the standard course after CS50 for Harvard CS concentrators, teaching functional programming in OCaml alongside design principles — abstraction, modularity, and multiple programming paradigms. It's where students go from making code work to making it well-designed.
CS 124 — Data Structures and Algorithms
CS 124 is Harvard's algorithms course — divide and conquer, greedy algorithms, dynamic programming, graph algorithms, hashing, and NP-completeness — combining rigorous analysis with programming assignments. It's a core theory requirement for CS concentrators and a known interview-prep powerhouse.
CS 61 — Systems Programming and Machine Organization
CS 61 is Harvard's systems programming course — C and C++, assembly, memory, caching, process control, and concurrency — and one of the two standard follow-ons to CS50 for CS concentrators. Its course site publishes lecture notes and problem sets publicly, so it also draws self-learners looking for a systems sequel to CS50.
CS 109A — Data Science 1: Introduction to Data Science
CS 109A — cross-listed as Stat 109A — is the first half of Harvard's data science sequence: data wrangling, exploratory analysis, regression, classification, and model evaluation in Python. Past course materials are published openly on the teaching team's site, giving it a large self-study audience beyond enrolled students.
CS 121 — Introduction to Theoretical Computer Science
CS 121 is Harvard's theory of computation course — computational models, Turing machines, uncomputability, and NP-completeness — taught from a free online textbook written for the course. It's the theory pillar of the CS concentration alongside CS 124.
CS 181 — Machine Learning
CS 181 is Harvard's core machine learning course — regression, classification, neural networks, clustering, graphical models, and reinforcement learning — with an emphasis on the probabilistic foundations beneath the methods. It's the standard ML credential inside the CS concentration.
Mathematics
MATH 55 — Studies in Algebra and Group Theory / Real and Complex Analysis
Math 55 (55A in fall, 55B in spring) is Harvard's legendary honors freshman math sequence, covering proof-based abstract algebra, group theory, and real and complex analysis at extraordinary speed and depth. It's widely described as the hardest undergraduate math class in the country.
MATH 1A — Introduction to Calculus
Math 1A is Harvard's introductory calculus course — limits, derivatives, integrals, and the Fundamental Theorem of Calculus — for students who didn't take or don't have credit for calculus before college. It leads into Math 1B and the rest of the math sequence.
MATH 21A — Multivariable Calculus
Math 21A covers multivariable calculus — vectors, partial derivatives, multiple integrals, and vector fields — and is the standard math course for Harvard students in sciences, economics, and pre-med tracks who arrive with single-variable calculus done.
MATH 21B — Linear Algebra and Differential Equations
Math 21B covers linear algebra — systems, matrices, eigenvalues, orthogonality — and applies it to differential equations and Fourier series. It's a workhorse requirement for applied math, economics, CS, and science concentrators.
MATH 25 — Theoretical Linear Algebra and Real Analysis
Math 25 (25A in fall, 25B in spring) is Harvard's honors first-year sequence in proof-based linear algebra and real analysis — the rigorous track below the legendary Math 55. It's the standard landing spot for strong students who want real mathematics at a survivable pace.
Statistics
STAT 110 — Introduction to Probability
Stat 110 is Joe Blitzstein's celebrated probability course — counting, conditional probability, random variables, distributions, expectation, and Markov chains — known for its storytelling style and brutal-but-beautiful problems. Its free lecture videos have made it a global staple for self-learners and quant-interview preppers.
STAT 111 — Introduction to Statistical Inference
Stat 111 is the sequel to Stat 110, turning probability into inference: estimators, maximum likelihood, confidence intervals, hypothesis testing, and Bayesian inference, taught with the same story-driven style. It's the second core course for statistics concentrators and a favorite of quant-leaning economics and CS students.
Economics
EC 10A — Principles of Economics: Microeconomics
Ec 10A is the fall-semester microeconomics half of Harvard's famous Principles of Economics sequence — historically one of the largest courses at the college. It covers supply and demand, markets, firm behavior, and policy applications, and is the entry point to the economics concentration.
EC 10B — Principles of Economics: Macroeconomics
Ec 10B is the spring macroeconomics half of Harvard's principles sequence: GDP, inflation, unemployment, growth, monetary and fiscal policy, and international economics. Together with Ec 10A it forms the foundation for all further economics coursework at Harvard.
EC 1010A — Intermediate Microeconomics
Ec 1010A is Harvard's intermediate microeconomic theory course — consumer and producer optimization, equilibrium, market failures, and welfare — and the first of the two theory pillars of the economics concentration after Ec 10. It's where economics goes from graphs to calculus.
EC 1010B — Intermediate Macroeconomics
Ec 1010B is Harvard's intermediate macroeconomic theory course — growth, fluctuations, unemployment, inflation, and the analytics of fiscal and monetary policy — the second theory pillar of the economics concentration after Ec 10. Models that Ec 10B sketched verbally get full mathematical treatment here.
Life Sciences
LS 1A — An Integrated Introduction to the Life Sciences: Chemistry, Molecular Biology, and Cell Biology
Life Sciences 1a is Harvard's integrated intro for pre-meds and life-science concentrators, weaving general chemistry, organic chemistry fundamentals, biochemistry, and molecular and cell biology into one fall-semester course. It's the standard first step in the life sciences sequence.
LS 1B — Genetics, Genomics, and Evolution
Life Sciences 1b is the spring half of Harvard's foundational life sciences year, covering genetics, genomics, and evolution — how variation arises, how it's inherited, and how populations change. With LS 1a it anchors the pathway into the life-science concentrations and pre-med requirements.
Physical Sciences
Chemistry
Physics
Government
Psychology
Expository Writing
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