What's the difference between emulation and simulation? [duplicate]

Answer 1

I do not know whether this is the general opinion, but I've always differentiated the two by what they are used for. An emulator is used if you actually want to use the emulated machine for its output. A simulator, on the other hand, is for when you want to study the simulated machine or test its behaviour.

For example, if you want to write some state machine logic in your application (which is running on a general purpose CPU), you write a small state machine emulator. If you want to study the efficiency or viability of a state machine for a particular problem, you write a simulator.

Answer 2

(Using as an example your first link)

You want to duplicate the behavior of an old HP calculator, there are two options:

1. You write new program that draws the calculator's display and keys, and when the user clicks on the keys, your programs does what the old calculator did. This is a Simulator

2. You get a dump of the calculator's firmware, then write a program that loads the firmware and interprets it the same way the microprocessor in the calculator did. This is an Emulator

The Simulator tries to duplicate the behavior of the device.
The Emulator tries to duplicate the inner workings of the device.

Answer 3

This is a hard question to answer definitively because the terms and often misused or confused.

Often, an emulator is a complete re-implementation of a particular device or platform. The emulator acts exactly like the real device would. For example, a NES emulator implements the CPU, the sound chip, the video output, the controller signals, etc. The unmodified code from a NES castridge can be dumped and then the resulting image can be loaded into our emulator and played.

A simulator is a partial implementation of a device/platform, it does just enough for its own purposes. For example, the iPhone Simulator runs an "iPhone app" that has been specifically compiled to target x86 and the Cocoa API rather than the real device's ARM CPU and Cocoa Touch API. However, the binary that we run in the simulator would not work on the real device.

Answer 4

An "emulator" is a term for a software-based hardware-simulator, but in general the two are synonyms.