Emulation

Emulation refers to the ability of software and/or hardware to imitate another program or piece of equipment. Emulation is particularly useful for running programs originally designed for another operating system, computer, printer, or even video-game console.

The basic emulation process is simple to understand. Assume that you are interested in using a program written for an Apple IIc, a very early computer. In order for your current computer to run the program, it must somehow trick the program into believing that it is an Apple IIc. The Apple IIc and your current computer use different chips and different instructions to tell the computer how to process information; an emulator converts the Apple IIc instructions into a set that your current computer can understand. The result is that the computer's processor and memory simulate the environment that was originally used to run the program.

In general, two types of emulators exist: interpretive and dynamic. Interpretive emulators interpret information as they access it, but once the instructions are executed, they are not stored. Since the information is not stored, it slows the emulation process, as every piece of information must be freshly converted. Dynamic emulators follow the same basic process as the interpretive ones; however, they also store information that is interpreted (if needed) for future use. This speeds the emulation process, although it places more of a strain on a system's memory capacity.

Although almost any type of hardware or software can be emulated, one of the best-known computer emulations was made by Apple, whose 1994 introduction of the PowerPC was hailed as a major advance in computing. It used emulation to simulate an Intel-based PC, allowing it to run Microsoft Windows and Windows-based software. Until the PowerPC's introduction, Mac users were unable to use PC-based programs, and cross-platform programs were just starting to be introduced to the mass market. The PowerPC introduced emulation to a new audience, and demonstrated its potential.

Emulation is also commonly used to take advantage of software written in specific formats, or with specific pieces of equipment in mind. For instance, it is common for most laser-jet printers to be able to emulate those created by Hewlett Packard (HP), due to the abundance of software available for the latter.

One of the most popular uses for emulators involves classic video games. The use of emulators to recreate the operating environments of early video-game consoles and machines on a PC has allowed long-time enthusiasts to reacquaint themselves with games from their past. Most of these games can now be located and downloaded quite easily on the Internet as Read-Only Memory (ROM) files, which contain the same information found on the original game cartridges, and which are translated by emulators to recreate the games. The Multiple Arcade Machine Emulator (MAME) is among the most popular and powerful video-game emulators available. MAME can emulate over 1,500 video games, including classics such as Asteroids, Defender, and Pac-Man.

Emulators such as MAME also bring to light various legal issues. For example, emulating a video game on a computer is legal only if you own a copy of that game, or if it has become part of the public domain. Since the games that MAME and other similar programs help to simulate are quite old, most companies do not threaten legal action over the downloading of their ROM files. Proprietors of newer games and consoles have been less lenient, however, and have pursued legal means to protect their games. Companies such as Sony have recently brought legal action against individuals and companies marketing PlayStation emulators, which could impact company sales profits.

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