Concept Algebra (CA) is a denotational mathematical structure for formal knowledge representation and manipulations in cognitive computing and machine learning. CA provides a rigorous and dynamic knowledge modeling and processing tool, which extends the informal, static, and application-specific ontological technologies. An operational semantics for the calculus of CA is formally elaborated using a set of computational processes in real-time process algebra (RTPA). A case study is presented on how machines and agents may mimic the key ability of human beings to autonomously manipulate knowledge using CA. This work demonstrates the expressive power and a wide range of applications of CA for both humans and machines in cognitive computing, semantic computing, machine learning, and computational intelligence.