Even before the first commercial computers appeared in 1951, "mass" storage, although minuscule by today's standards, was a necessity. As early as the mid-1800s, punch cards were used to provide input to early calculators and other machines. The 1940s ushered in the decade when vacuum tubes were used for storage until, finally, tape drives started to replace punch cards in the early 1950s. Only a couple of years later, magnetic drums appeared on the scene. In 1957, the first hard drive was introduced as a component of IBM's RAMAC 350. It required 50 24-inch disks to store five megabytes of data and cost roughly $35,000.