An introduction to Emulation 1/2/3/4
On this page I'll try to introduce newcomers to the world of Emulation. I doubt there are people who use computer and haven't heard about emulation. What is emulation? Emulation is 'emulating' the hardware of a machine, computer or gameconsole through software, so that the computer the software runs on thinks it is the emulated machine. So, an emulator is a computer program. Emulation can also be done trough hardware, or a combination of hard- and software. Not always are all features of the emulated machine emulated, or are only games emulated. As an example, Neill Corlett's Highly Experimental is an emulator in plugin form that emulates the sound processor of a Playstation. It can play dumped sound data of Playstation games. Anyway, with a Super NES emulator, the PC emulates the SNES hardware so the PC thinks it's a SNES. This makes the emulator capable of running software specifically designed for that machine, or in this case gameconsole. Most of the time however, the software can't be played the 'normal' way. You can't insert a SNES gamecart in your PC. So, the actual game information inside the ROM chips of the SNES cart need to be transferred in a way it'll be readable for the PC. Luckily many devices were and are still developed in the Far East, that makes it possible to connect the gamecart to that device. The device is connected to a PC (or it has a floppydrive/cd-burner built in), so the information inside the ROM chips can be transferred to a file on the harddisk (or floppy/CD-ROM). This transferring is also called ROM dumping. You now have a ROM dump of the game on your PC! ROMs have different extentions (like .txt for text files). There are certain standards for different ROMs, but some extensions are shared by different ROMs (by which I mean ROMs for different systems. For example, .bin and .rom are commonly used for ROMs. Some extension examples to give you an idea; .nes is used for NES ROMs, .smc for SNES, .v64 is an example of an N64 ROM extension. Mostly the extensions are chosen wisely; .smc stands for Super MagiCom, the device used to dump the ROM. Alternatively .swc is also existant for SNES, which stands for Super WildCard, another similar device.
The emulator again, is often designed to run these ROM images. This way, the emulator can run the software for the emulated system. Unfortunately, dumping ROM images is seen as illegal. In order for emulation to be 100% legal, the software must be run from the original media, in this case the gamecart. Unfortunately this isn't possible at all with the SNES, and many other systems. So in order to be able to play SNES games on your PC you must use ROM images. It's different with for example the Playstation (PSX), which uses CD-ROMs which are readable by a PC. Playstation games can thus be run 100% legal on an emulator, but only if you use original PSX CD-ROMs.
ZSNES before loading a ROM image.
Back to the SNES then. The SNES is by long dead and you can't buy the games anymore, unless you buy used games from someone, which are becoming rare. So how can you make the ROM images then? Luckily the Internet is widely used to spread ROM images of games, but it's ILLEGAL! Because of that, ROM images (or just plain ROMs) can't always be found easily, just like MP3's. I'm not here to guide you finding ROMs, and don't bother to ask me either.
There are hundreds of ROMs to be found on the Internet, and not all of them are in a good state. You see, ROMs can be dumped badly as well resulting in bad (corrupt, non or not well working ) ROMs. But some people in the emulation community developed (and still do) tools to identify your ROMs to see if they're bad or good. Cowering is one of the best known people to create these tool, the Good Tools. Good Tools are different for each system ROMs exist of. For example, the Good Tool for SNES is called GoodSNES. You also have GoodNES, GoodN64, etc., etc. These tools identify the ROMs mainly by their CRC (Clyclic Redundancy Check) value. The CRC value is a unique value each file on your PC has. For example, a ROM can have a CRC of 7BDC6A78. CRC values consist of a 8 token hexadecimal value. If a known good ROM has this value, and the ROM you scan with e.g. GoodSNES has a different value, it's most likely corrupt (if it's the same game, that is.).
The Good Tools can also rename your ROMs, so you can easily see which game it is, what country it's from, etc. For example, a SNES ROM file called SuperMarioWorld.smc can be renamed to Super_Mario_World_(U)[!].smc. For more info about what the tokens between brackets mean, click here. It's basically a universally accepted naming convention for ROMs. There are alternative naming systems, but Cowering's one is the most used one. Good Tools are really needed when messing with ROMs, and they can do a lot more than what I just wrote. They can be found here, and a tutorial can be found here. Because they are commandline utilities, they can be very unfriendly for newcomers or people with little computer (or DOS) experience. Master of Puppets has created a frontend (GUI) for the tools, which can be found here. ROMs are usually zipped to save space. So, Super_Mario_World_(U)[!].smc becomes Super_Mario_World_(U)[!].zip with the .smc file inside.