Below the Code

OS & Networks

The systems layer of computer science — how one machine runs your program (processes, memory, scheduling) and how millions of machines talk to each other (TCP/IP, HTTP, DNS). The knowledge every other track quietly depends on.

32Guides live
4Pillars complete
8Quizzes each
100%Interview-relevant
Four pillars

All four pillars are complete — eight full guides each, thirty-two in total.

8 guides live
Operating Systems
processes · memory · scheduling
What actually happens when you run a program — processes vs threads, virtual memory, CPU scheduling, filesystems, and the concurrency bugs interviewers love.
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Roadmap live
Networking
TCP/IP · HTTP · DNS
What happens when you type a URL — the TCP/IP stack, HTTP/S, DNS resolution, sockets, and the handshakes underneath every request your apps make.
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8 guides live
Security
authn · crypto · OWASP
Authentication vs authorization, hashing and TLS, the OWASP top 10, and how real attacks work — the defensive layer every production system needs.
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8 guides live
Theory of Computation
automata · complexity
Finite automata, regular expressions under the hood, Turing machines, and P vs NP — why some problems are hard no matter the hardware.
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Browse the systems roadmaps Operating systems, networking, security and theory of computation each have their own roadmap. Explore →
Why this section exists
01System design assumes it — you can't reason about load balancers without TCP, or containers without processes.
02Interviews probe it — "what happens when you type a URL" and "process vs thread" are evergreen questions.
03Debugging lives here — memory leaks, port conflicts, DNS failures: the systems layer is where prod issues hide.