Simulator or Emulator? What is the difference?

Question

While I understand what simulation and emulation mean in general, I almost always get confused about them. Assume that I create a piece of software that mimics existing hard

Answer 1

Simulation = For analysis and study

Emulation = For usage as a substitute

A simulator is an environment which models but an emulator is one that replicates the usage as on the original device or system.

Simulator mimics the activity of something that it is simulating. It "appears"(a lot can go with this "appears", depending on the context) to be the same as the thing being simulated. For example the flight simulator "appears" to be a real flight to the user, although it does not transport you from one place to another.

Emulator, on the other hand, actually "does" what the thing being emulated does, and in doing so it too "appears to be doing the same thing". An emulator may use different set of protocols for mimicking the thing being emulated, but the result/outcome is always the same as the original object. For example, EMU8086 emulates the 8086 microprocessor on your computer, which obviously is not running on 8086 (= different protocols), but the output it gives is what a real 8086 would give.

Answer 2

If a flight-simulator could transport you from A to B then it would be a flight-emulator.

An emulator can replace the original for real use.
A Virtual PC emulates a PC.

A simulator is a model for study and analysis.

An emulator will always have to operate close to real-time. For a simulator that is not always the case. A geological simulation could do 1000 years/second or more.

Answer 3

To understand the difference between a simulator and an emulator, keep in mind that a simulator tries to mimic the behavior of a real device. For example, in the case of the iOS Simulator, it simulates the real behavior of an actual iPhone/iPad device. However, the Simulator itself uses the various libraries installed on the Mac (such as QuickTime) to perform its rendering so that the effect looks the same as an actual iPhone. In addition, applications tested on the Simulator are compiled into x86 code, which is the byte-code understood by the Simulator. A real iPhone device, conversely, uses ARM-based code.

In contrast, an emulator emulates the working of a real device. Applications tested on an emulator are compiled into the actual byte-code used by the real device. The emulator executes the application by translating the byte-code into a form that can be executed by the host computer running the emulator.

To understand the subtle difference between simulation and emulation, imagine you are trying to convince a child that playing with knives is dangerous. To simulate this, you pretend to cut yourself with a knife and groan in pain. To emulate this, you actually cut yourself.

Answer 4

Simulator is something more broader than Emulator and it seems like the duality of this terms is overthought in the posts above.

Emulator

People decided to use a new word emulation in the "computer world" when they started replacing some hardware parts of the existing system in straightforward manner - imitating their behaviour and relying on the computational nature to be sure to not break something and leave everything in the equivalent state. So we have emulated the piece of this! (and the whole still works as before)

Emulator usually used in narrow sense in digital area as replacement and virtualization - presenting in digital form as a piece of software - of something known and existed before (virtual chips, circuit boards, electronic devices). So when the world became more digital and brought the emulator word to the masses, the masses added uncertainty to it (or additional reasons).

Simulator

First of all, I saw many comments about emulators do or replace something real but simulators not.

BUT flight simulator is used for a real thing - it trains pilots, gives them skill up and knowledge and it replaces expensive real planes and saves much of money. And we cannot just say a plane-emulator because we have inner feeling that this is much more than that, so we call it simulator :) Plane simulator could contain emulated radar or transponder that is true.

Contra-statements that simulators are used for analysis and study (and emulators for something real), but that analysis and study not less a real thing than emulated GSM boards (even more in the informational age we live in). Analysis adds a value to the business, cuts costs or points out to profits not less than the replaced (emulated) hardware.

Simulator is similar to modelling of something that we can't obtain for some reason (cost, technology, physical impossibility). It is usually simulated for something new or intangible or complex or not properly known to us like market, weather, combustion, user. So here comes the flight, black hole, stock exchange, simulations.

So finally:

1. Simulator is broader than Emulator
2. Simulator tends to imitate/model more global processes/things in general with ability to narrow the imitation down (e.g. capacitor simulator with presets representing some known models)
3. Emulator tends to imitate certain hardware devices with certain specification, known characteristics and properties (e.g. SNES emulator, Intel 8087 or Roland TB-303)

As for words origin

All came from Latin and mean:

• emulate is "to be equal" (looks like more aggressive and straightforward - rivalry)
• simulate is "to be similar" (looks like more sly and tricky - imitation)

Answer 5

An emulator is a model of a system which will accept any valid input that that the emulated system would accept, and produce the same output or result. So your software is an emulator, only if it reproduces the behavior of the emulated system precisely.

Answer 6

An emulator is an alternative to the real system but a simulator is used to optimize, understand and estimate the real system.