CCW-based channels include parallel, ESCON, and FICON channels. A CCW can also be used to talk to an OSA card (this is discussed further in the topic on Open Systems Adaptor, OSA).

The CCW is the original I/O operation used for communications with the channel subsystem. The CCW contains a channel command, such as read, write, or control, along with the data address of the data area involved. The data is passed to the channel subsystem. The channel subsystem communicates status of the I/O back to the issuing application. When a channel communicates with an application in an asynchronous fashion, it is referred to as a channel interrupt.