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CAD (Computer Aided Design)
Programs used to design architectural, mechanical and electrical engineering drawings.
CAM (Computer Aided Manufacturing)
Programs used to control manufacturing equipment.
CIM (Computer Integrated Manufacturing)
A term used for describing a high level of automation in a manufacturing enterprise.
COM (Component Object Model)
COM Component Object Model, is a family of Microsoft specifications and software that produces platform independent, object-oriented and scalable components. It is the "glue" that integrates the operating environment with plant applications and supports the inter-operability of applications, devices and systems. COM compliant interfaces are built into applications and "glued" together using the COM services and the Windows infrastructure.
CPU (Central processing unit)
Microprocessor portion of the PLC. It is the portion of the PLC that handles the logic.
CNC (Computer Numerical Control)
Allows the control of motion in an accurate and programmable manner through use of a dedicated computer within a numerical control unit, with a capability of local data input such that machine tools are freed from the need for "hard-wired" controllers.
Compare instruction
PLC instruction that is used to test numerical values for equal, greater than, or less than relationships.
Contact
Symbol used in programming PLCs. Used to represent inputs. There are normally open and normally closed contacts. Contacts are also the conductors in electrical devices such as starters.
Contactor
Special-purpose relay that is used to control large electrical current.
Current sinking
Refers to an output device that allows current flow from the load through the output to ground.
Current sourcing
Output device that allows current flow from the output through the load and then to ground.
Client-Server Architecture
The underlying philosophy of centralized processing. In multiple computer systems it can be more efficient for only one computer (the server) to perform certain operations. When another computer requires the data, no processing or synchronization is required, the data is merely requested from the server.
Cycle time
Time required to perform the cycle. (ISO 8373)
CRC (Cyclic Redundancy Check)
A calculated value, based on the content of a communication frame. It is inserted in the frame to enable a check of data accuracy after receiving the frame across a network. BITBUS uses the standard SDLC CRC.
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