Computer Science

Binary Numbers

Bits, place value, and carry — how a machine counts in base 2.

Two's Complement

How signed integers really work

Floating Point (IEEE 754)

Sign, exponent, mantissa visualized

Boolean Logic & Gates

AND/OR/NOT and digital circuits

Instruction Execution

Fetch, decode, execute — one instruction's trip through the CPU.

CPU Pipeline

Five stages overlap so an instruction finishes almost every cycle — until a data hazard stalls the pipeline.

Branch Prediction

Speculative execution and misprediction cost

Cache Hierarchy

L1/L2/L3, locality, cache lines

Process Scheduling

FCFS, SJF, and Round Robin on a Gantt chart

Multi-Level Feedback Queue

Round-robin, priority queues, I/O, and aging boost

Virtual Memory

Paging, page table, TLB

Page Replacement

FIFO, LRU, Clock, Bélády's anomaly

Threads & Synchronization

Race conditions, mutex, and deadlock

File Systems

inode, directory entry, link count

OSI / TCP-IP Model

Layered network architecture walkthrough

TCP Handshake

Three-way handshake, sequence numbers, retry

TCP Connection Teardown

Four-way handshake, FIN/ACK, TIME_WAIT

Congestion Control

Textbook Reno: slow start, AIMD, timeout

HTTP / HTTP/2 / HTTP/3

Request-response, multiplexing, QUIC

TLS Handshake

Certificate, key exchange, encryption

DNS Resolution

Recursive vs. iterative lookup

Routing Protocols

A stale DV cost loops; a link-state map drops

SQL Joins

INNER, LEFT, FULL — watch rows match, miss, and fill with NULL.

GROUP BY & Aggregation

Rows fall into buckets, buckets collapse into aggregates.

Window Functions

A frame slides over ordered rows — running totals and ranks without collapsing.

B+ Tree

Watch leaf copies, internal pushes, and linked-leaf range scans.

LSM Tree

See fast writes defer sorting and merging while sequence rules keep overlapping versions correct.

MVCC

Watch snapshots choose row versions while readers overlap updates and cleanup waits.

Database Indexing

Watch scans, hash buckets, B+ tree leaves, and covering payloads trade page reads.

Raft Consensus

Leader election and log replication

Two-Phase Commit

Distributed transaction coordination

Consistent Hashing

Hash ring with virtual nodes

Lexer & Parser

Tokenization and AST construction

AST → Code

Tree walker, IR, optimization passes

Virtual Machine

Bytecode execution and JIT

Git's Four Areas

Move one change through the working tree, index, local repository, and remote.

Commits as Snapshots

A commit records the staged snapshot, its parent, and a new identity.

Branches & HEAD

Branches move with new commits; HEAD marks which reference moves next.

Fast-Forward Merge

When history has not diverged, merge advances a branch without creating a commit.

Three-Way Merge

Combine two diverged histories through their common ancestor and a two-parent commit.

Merge Conflicts

Resolve competing edits, stage the result, and finish the interrupted merge.

Remote Collaboration

See exactly what fetch, pull, and push change across local and remote repositories.

Tags & Releases

Commits advance branches, not tags; annotated tags add an object, and checkout detaches HEAD.

Rebase

Replay commits onto a new base and watch every copied commit receive a new ID.

Undoing Changes

Compare restore, reset, and revert by the repository layer each one changes.