Apple often gets credit for starting the personal computer revolution, but the Macintosh, which debuted in 1984, was not the original mass-market PC. On Aug. 12, 1981, IBM launched the 5150 and changed home and office life forever. The system packed a 4.77-MHz Intel 8088 processor and up to 256 KB of memory, weighed 25 pounds with "diskette" drive, and sold for $3,000. It wasn't unreasonably bulky or expensive, and its boxy form factor remains the standard for PCs. Legions of schoolchildren and small-business employees began learning the already popular VisiCalc spreadsheet along with a new operating system called DOS. Starting in 1983, on-the-go professionals opted for a Compaq, the first fully compatible PC clone and the first portable clone. Windows, multi-gigabyte hard drives, the internet and the 3-pound laptop followed. It all started here.
http://blog.wired.com/ wiredphotos6/2006/12/ 9_ibm_5150_pers.html