The basic purpose of CAMAC is to provide a standardized method for transmitting data and control information between instrumentation modules and a digital controller. CAMAC encompasses both a hardware standard for housing the modular components of a system and an electrical and logical standard for the control "language" used in the transfer of digital information. The CAMAC specification contains the rules for both of these aspects of CAMAC. This paper describes the features and uses of the control language in a less formal way than must be used in the specification. Examples are given of the interplay of control and synchronization signals between the modules concerned. Other papers in this series consider other aspects of CAMAC, including its place in the context of instrumentation systems, hardware aspects, signal standards, the Branch Highway, and coupling to computers and control systems. Here, the scope is limited to the process of information interchange within the CAMAC crate. This paper is designed to supplement the CAMAC specification. The reader is advised to obtain a copy of that document, and to read it first. The reader's attention is also called to other references containing informal descriptions ot the CAMAC system.