# C/C++ Library Interfaces¶

An underlying philosophy in the development of Sage is that it should provide unified library-level access to the some of the best GPL’d C/C++ libraries. Sage provides access to many libraries which are included with Sage.

The interfaces are implemented via shared libraries and data is
moved between systems purely in memory. In particular, there is no
interprocess interpreter parsing (e.g., `pexpect`

),
since everything is linked together and run as a single process.
This is much more robust and efficient than using `pexpect`

.

Each of these interfaces is used by other parts of Sage. For example, eclib is used by the elliptic curves module to compute ranks of elliptic curves and PARI is used for computation of class groups. It is thus probably not necessary for a casual user of Sage to be aware of the modules described in this chapter.