IBM 350 Disk Storage Unit

IBM introduced the world's first magnetic hard disk for data storage, the RAMAC (or Random Access Method of Accounting and Control), in 1956. The IBM 350 Disk Storage Unit offered unprecedented performance for its time by allowing random access to any of the million characters distributed over both sides of 50 two-foot-diameter disks containing 50,00 sectors -- each of which held 100 alphanumeric characters. The hard disk stored about 2KB of data per square inch and had a purchase price of about $10,000 per megabyte.