A note on the history of Shift-JIS, as opposed to the older JIS
The first Japanese character encoding used on computers was JIS X 0201, which replaced the ASCII characters over 127 with tiny katakana characters called hankaku kana. Early Japanese computers could only print Roman letters and these ugly half-width katakana, which are still seen today on receipts, invoices, and the like. When JIS was upgraded to JIS X 0208, the half-width katakana were replaced with other characters.
Microsoft decided to bring back the half-width katakana to make their version of JIS compatible with older JIS X 0201 files, so they shifted the entire set over 127 places: hence the name "Shift-JIS." Shift-JIS is identical to regular JIS, except that all the characters after the standard ASCII are moved forward 127 values. (BTW, this is why accented European characters tend to farg up on Japanese computers.)
For more info on Japanese character encoding, I strongly recommend Jim Breen's guide at http://www.csse.monash.edu.au/~jwb/coding_inf.html.