Callee

Callee is a term used in several related domains to denote the party that is being called or invoked. In everyday language and telecommunications, the callee is the person or device at the receiving end of a call, as opposed to the caller who initiates the connection. The callee can be a human user, a voicemail system, or an automated response system that answers and participates in the communication.

In computer science, callee refers to the function or subroutine that is invoked by another function, known as the caller. The callee executes the requested operation and typically returns a value to the caller. The interaction between caller and callee is governed by a calling convention, which specifies how arguments are passed, how results are returned, and which resources (such as registers) must be preserved by the callee.

Within programming practice, the concept of callee is important for understanding control flow and resource management. Some calling conventions designate certain registers as callee-saved, meaning the callee must preserve their values across the call. The callee is also responsible for setting up and tearing down its stack frame, unless optimizations like tail calls reuse the caller’s frame.

Etymology and usage: callee is formed from the verb call plus the -ee suffix, indicating the recipient of an action. The term is widely used in both telecommunications and programming contexts, sometimes with domain-specific nuances.

See also: caller, calling convention, stack frame, callee-saved registers, tail call, telecommunications.