An emulator is a program that replicates one processor, computer, or system on another. The system that runs the emulator usually must be more powerful than the original system. Believe it or not, only recently have personal computers become powerful enough to emulate the video game consoles of the 1970s and 1980s. Most of the emulators I'll discuss require a 486 processor at minimum. This time, I'll cover shareware and freeware emulators available on the Internet. Freeware refers to software that you can obtain at no cost. Shareware is software you can download and try before you pay for it. Next time, I'll cover commercial emulators available in stores.
Note that all emulators require you have copies of the game cartridges (called ROM images) on your computer in order to play the games. It is illegal to own a copy of a commercial game you do not have in actual cartridge (or other original) format. I am not even entirely sure of the legality of having ROM images of games you do own. Although there are many Internet sites to get ROM images, I will not discuss them here nor in e-mail, so please don't bother to ask. This does not apply to the new shareware and freeware games I have discussed in a previous article.
The most popular classic system, the Atari 2600, has also spawned the most emulators. Probably the most complete one is PC Atari, which runs under MS-DOS. One of the nicer features is a built-in front-end, which makes selecting the game you want to play easier. Most other emulators require you to specify the ROM image on the command line when you invoke it. This includes Stella, another fairly complete emulator which runs on UNIX, MS-DOS, Windows 95/NT (although the latest version isn't available for Windows yet), OS/2, and Power Macs. One feature Stella has that PC Atari lacks, however, is support for Supercharger games. Stella, like PC Atari, is still being updated with new features. Some other Atari 2600 emulators are Virtual 2600, which has versions that run on UNIX, MS-DOS, Amiga platforms, and A26 and VCS 2600, both for MS-DOS.
There are three Atari 5200 emulators. One of the oldest is Rainbow, which began as an Atari 400/800 computer emulator on the Macintosh. (The Atari 5200 is actually an Atari 800-type computer with some modifications.) There is now a version for Windows 95 and NT as well. The other two emulators are both for DOS and are called Pokey, which also emulates Atari computers, and Virtual Super System (VSS).
Marat Fayzullin is, as far as I know, the only person to write a Colecovision emulator. It is called simply ColEm. There are versions for MS-DOS, Macs, UNIX, Windows, and OS/2, although not all are up to date. The emulator is fairly complete, so Mr. Fayzullin has not made any updates since 1996. There is also only one Vectrex Emulator. It is called DVE, which stands for DOS Vectrex Emulator. It is also mostly complete and has not been updated recently. Note that what I said about copying ROM images does not apply to the Vectrex because the copyright holder has released them for copying for non-profit purposes.
If you get tired of having to remember funny file names for different cartridges, you might try a front-end program that lets you pick cartridges from a menu. One I have used with DVE is Console Menu, which can be used with several different emulators.
Copyright 1997 i5ive communications inc. Used with permission.
[April 28, 2013: PC Atari Emulator is still available and now has a Windows version. Stella, however, is probably the dominant Atari 2600 emulator now. Virtual 2600 is available, but no longer being maintained. Official sites for A26 and VCS 2600 no longer seem to exist.
ColEm is still around. DVE can be found, but doesn't seem to have a site of its own. ParaJVE, a Vectrex emulator written in Java became a DVE competitor.
However, pretty much all these systems are now emulated by one emulator called MESS (Multi Emulator Super System).]