Agraph
From Agraph Tutorial [PDF] by Stephen C. North:
Agraph is a C library for graph programming, It defines data types and operations for graphs comprised of attributed nodes, edges, and subgraphs. Attributes may be string name-value parirs for convenient file I/O, or internal C data structures for efficient algorithm implementation
Agraph library is a part of GraphViz.
Ch
From The Ch Language Environment—SDK User’s Guide, version 5.1 [PDF]
Ch is an embeddable C/C++ interpreter. Ch supports all features in the ISO 1990 C standard, most new features in the latest ISO C99 standard including coplex and variable length arrays, lasses in POSIX, C++, Win32, X/Motif, OpenGL, GTG+, ODBC, WinSock, very high-level shell programming, corss-platform internet computing in safe Ch, computational arrays for linear algebra and matrix computations, high-level 2D/3D plotting and numerical computing such as differential equation solving, integration, Fourier analysis. Ch can also be used as a login Unix command shell and for high-level scripting such as shell programming to automate tasks and common gateway interface in a Web server in both unix and Windows.
ChAgraph
ChAgraph is the Ch interface to Agraph library. It provides access to most of the Agraph library features so programs using it can be conveniently executed in Ch space. With Agraph it is possible to perform I/O perations, modifications or building of graphs from Ch scripts. Together with other GraphViz libraries (libdot, libneato, libtwopi, libgraph, etc) it is also possible to control graph drawing from Ch space or even write complete graph drawing driver as Ch script.