In a data transmission, what is the term used for the computer that originates the message?

The term that refers to the computer originating the message in a data transmission is "Sender." This is the device that initiates the communication process by creating and sending a message across a network or to another computer. The sender plays a crucial role in transmitting data, as it encodes the information and uses the appropriate protocols to communicate effectively with the receiving end.

A "Channel" refers to the medium through which the message travels, such as cables or wireless signals, but does not pertain to the origin of the message itself. The "Receiver" is the recipient of the message, not the source, and "Protocol" is a set of rules that governs how data is transmitted and received, but is not a physical entity involved in the origin of the message.