libquantum is a C library for the simulation of quantum mechanics, especially of quantum computing. It provides a structure for a quantum register (the memory of a quantum computer) and operations for the manipulation of a quantum register.
This documentation describes how to use libquantum to build quantum circuits for quantum computing. For an introduction to the field you should use a textbook such as [Nielsen, 2000].
The following sections contain the API documentation for libquantum 1.1.1. For the latest versions of libquantum and of this documentation, take a look at http://www.libquantum.de/.