cddlib is a C implementation of the Double Description Method of Motzkin et al. for generating all vertices (i.e. extreme points) and extreme rays of a general convex polyhedron in R^d given by a system of linear inequalities.

CUDD is a package for the manipulation of Binary Decision Diagrams (BDDs), Algebraic Decision Diagrams (ADDs) and Zero-suppressed Binary Decision Diagrams (ZDDs).

C-XSC is a libary for the development of numerical algorithms that deliver highly accurate and automatically verified results. C-XSC can do real, complex, interval, and complex interval arithmetic with mathematically defined properties, dynamic vectors and matrices, accurate dot products, predefined arithmetic operators with highest accuracy, standard functions of high accuracy, dynamic multiple-precision arithmetic and rounding control for the input and output of data.

FLINT (Fast Library for Number Theory) is a C library in support of computations in number theory. It is also a research project into algorithms in number theory. At this stage, FLINT consists mainly of fast integer and polynomial arithmetic and linear algebra.