Hard disk drive

The first hard disk drive was the IBM 350 Disk File, invented by Reynold Johnson and introduced in 1955 with the IBM 305 computer. This drive had fifty 24 inch platters, with a total capacity of five million characters. A single head was used for access to all the platters, making the average access time very slow. The IBM 350 Disk File was about the size of two refrigerators and was marketed as an accounting system.