This repository contains the complete source code for SQLite, a self-contained, high-reliability, embedded SQL database engine. The codebase implements a full SQL database system including a SQL parser (generated by the included Lemon parser generator), a bytecode virtual machine (VDBE) for executing prepared statements, a B-tree storage engine, a transaction manager with WAL and journaling, and a pluggable VFS (Virtual File System) layer for OS abstraction. The architecture is a monolithic C library designed for embedding into applications, with optional loadable extensions for full-text search (FTS3/4/5), R-tree spatial indexing, JSON processing, vector similarity search (vec1), and dozens of utility functions. Key entry points include the public C API defined in sqlite3.h, the command-line shell (shell.c), and the Tcl test harness. Data flows through the SQL parser to the query optimizer (where.c), which generates VDBE bytecode executed by the virtual machine, ultimately reading/writing pages through the pager and B-tree layers. External dependencies are minimal: only standard C library and optional ICU for Unicode support. The repository also includes extensive test suites, fuzz testing harnesses, and build systems for Unix, Windows, and WebAssembly.