Unfortunately, years of effort have gone into optimizating SQLite, both
for small size and high performance.  And optimizations tend to result in
complex code.  So there is a lot of complexity in the SQLite implementation.

Key files:

  *  **sqlite3.h** - This file defines the public interface to the SQLite
     library.  Readers will need to be familiar with this interface before
     trying to understand how the library works internally.

  *  **sqliteInt.h** - this header file defines many of the data objects
     used internally by SQLite.

  *  **parse.y** - This file describes the LALR(1) grammer that SQLite uses
     to parse SQL statements, and the actions that are taken at each stop
     in the parsing process.

  *  **vdbe.c** - This file implements the virtual machine that runs
     prepared statements.  There are various helper files whose names
     begin with "vdbe".  The VDBE has access to the vdbeInt.h header file
     which defines internal data objects.  The rest of SQLite interacts
     with the VDBE through an interface defined by vdbe.h.
................................................................................

  *  **pager.c** - This file contains the "pager" implementation, the
     module that implements transactions.

  *  **os_unix.c** and **os_win.c** - These two files implement the interface
     between SQLite and the underlying operating system using the run-time
     pluggable VFS interface.













## Contacts

The main SQLite webpage is [http://www.sqlite.org/](http://www.sqlite.org/)
with geographically distributed backup servers at
[http://www2.sqlite.org/](http://www2.sqlite.org) and
[http://www3.sqlite.org/](http://www3.sqlite.org).

Unfortunately, years of effort have gone into optimizating SQLite, both
for small size and high performance.  And optimizations tend to result in
complex code.  So there is a lot of complexity in the SQLite implementation.

Key files:

  *  **sqlite.h.in** - This file defines the public interface to the SQLite
     library.  Readers will need to be familiar with this interface before
     trying to understand how the library works internally.

  *  **sqliteInt.h** - this header file defines many of the data objects
     used internally by SQLite.

  *  **parse.y** - This file describes the LALR(1) grammer that SQLite uses
     to parse SQL statements, and the actions that are taken at each step
     in the parsing process.

  *  **vdbe.c** - This file implements the virtual machine that runs
     prepared statements.  There are various helper files whose names
     begin with "vdbe".  The VDBE has access to the vdbeInt.h header file
     which defines internal data objects.  The rest of SQLite interacts
     with the VDBE through an interface defined by vdbe.h.
................................................................................

  *  **pager.c** - This file contains the "pager" implementation, the
     module that implements transactions.

  *  **os_unix.c** and **os_win.c** - These two files implement the interface
     between SQLite and the underlying operating system using the run-time
     pluggable VFS interface.

  *  **shell.c** - This file is not part of the core SQLite library.  This
     is the file that, when linked against sqlite3.a, generates the
     "sqlite3.exe" command-line shell.

  *  **tclsqlite.c** - This file implements the Tcl bindings for SQLite.  It
     is not part of the core SQLite library.  But as most of the tests in this
     repository are written in Tcl, the Tcl language bindings are important.

There are many other source files.  Each has a suscinct header comment that
describes its purpose and role within the larger system.


## Contacts

The main SQLite webpage is [http://www.sqlite.org/](http://www.sqlite.org/)
with geographically distributed backup servers at
[http://www2.sqlite.org/](http://www2.sqlite.org) and
[http://www3.sqlite.org/](http://www3.sqlite.org).