An emulator is a program that allows a terminal or computer to behave like another system.
Thus, with an emulator, a microcomputer can emulate or imitate a much larger system, such as an IBM mainframe. The small computer then runs the same programs as the large one and works with the same types of data. When two computers communicate, they must be compatible. Emulator software is one way to establish the necessary compatibility.
According to DIN 44300, an emulator is a functional unit realized by program modules and construction units, which simulates the characteristics of a computer A on a computer B in such a way that programs for A can run on B, whereby the data for A are accepted by B and the same results as on A are obtained. What is said here about programs applies analogously also to the cooperation of hardware devices.