Which concept defines what it means for a function to be computable?

The concept of a Turing Machine is foundational in computer science and defines what it means for a function to be computable. A Turing Machine provides a theoretical model of computation that can simulate any algorithm or computable function. It consists of an infinite tape (which serves as memory), a head that reads and writes symbols on the tape, and a set of rules that dictate its operations based on the current symbol being read.

A function is considered computable if a Turing Machine can be constructed that, given an input, will produce the corresponding output in a finite amount of time. This foundational concept is crucial because it establishes the limits of what can be computed and helps in understanding the nature of algorithms and computation itself. By defining computability in this way, we can explore the boundaries of automated processes, algorithms, and more advanced fields like complexity theory.

The other concepts, while integral to computer science, do not specifically define computability. For instance, the Turing Test is focused on evaluating a machine's ability to exhibit intelligent behavior, binary coding pertains to how data is represented in a computer system, and digital encryption deals with the security of data rather than its computability.