QAC means Quality Assurance and Control.
The software was originally developed in 1986 by UK-based Programming Research Limited (PRQA) for the C language.
[1] Helix QAC was used to make the C source code measurements given in the book Safer C by Les Hatton.
The tools operate through an integrated development environment (IDE) designed to help maintain and understand old and new code using detailed cross references and a variety of graphical views.
The tools can be used with a command line interface, and graphical IDE can be called to display the result.