This is my old project (from 2004-2005 years), which implements arbitrary
precision integer arithmetic. The code is provided as-is, without
any modifications since the 2005 year.

It consists of the following parts:

* A C library for arbitrary presision arithmetic. It is located
  in the libbig_int folder.

* A command-line simple calculator based on the libbig_int. It is located
  in the libbig_int/projects/calc folder.

* A PHP wrapper for libbig_int library. It is located in the root folder.
  The wrapper is published at http://pecl.php.net/package/big_int .

* Crypt_RSA - a PoC implementation of RSA encryption and code signing in PHP.
  It is located in the PEAR folder. The implementation is published
  at http://pear.php.net/package/Crypt_RSA .