IBM RAMACIBM announces the IBM 305 RAMAC (Random Access Memory Accounting) mainframe, a computer as large as two refrigerators, containing the new 350 Disk Storage Unit, the world’s first hard disk drive. The nearly-six-foot-high drive consists of a huge metal case surrounding a towering stack of 50 double-sided magnetic platters, adding up to a total capacity of four megabytes. In 1958, IBM will introduce the option to double capacity by adding a second stack of drive platters to the casing. The 305 RAMAC and 350 Disk Storage Unit together weigh over a ton, and are leased to IBM’s clients for $3,200 per month.