See Fortran Callbacks

“callback function - one whose address is supplied for the purpose of being invoked when some anticipated event occurs. Opaque enums (669)” (EMCppSfe 2021)

Also called callback function

Snippet from Wikipedia: Callback (computer programming)

In computer programming, a callback is a function that is stored as data (a reference) and designed to be called by another function – often back to the original abstraction layer.

A function that accepts a callback parameter may be designed to call back before returning to its caller which is known as synchronous or blocking. The function that accepts a callback may be designed to store the callback so that it can be called back after returning which is known as asynchronous, non-blocking or deferred.

Programming languages support callbacks in different ways such as function pointers, lambda expressions and blocks.

A callback can be likened to leaving instructions with a tailor for what to do when a suit is ready, such as calling a specific phone number or delivering it to a given address. These instructions represent a callback: a function provided in advance to be executed later, often by a different part of the system and not necessarily by the one that received it.

The term callback can be misleading, as it does not necessarily imply a return to the original caller, unlike a telephone callback.

Mesa programming language formalised the callback mechanism used in Programming Languages. By passing a procedure as a parameter, Mesa essentially delegated the execution of that procedure to a later point in time when a specific event occurred, similar to how callbacks are implemented in modern programming languages.

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