A hard disk drive is a data storage device that stores data on a magnetic surface layered onto hard disk platters. A hard disk uses rotating platters (disks) to store data. Each platter has a smooth magnetic surface on which digital data is stored. Information is written to the disk by applying a magnetic field from a read-write head that flies very close over the magnetic surface. A typical hard disk drive design consists of a spindle on which the platters spin at a constant RPM. Moving along and between the platters on a common arm are read-write heads, with one head for each platter surface.

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 1301 Disk Storage Unit Control System Meganical International System, announced in 1961, introduced the usage of a separate head for each data surface. The first disk drive to use removable media was the IBM 1311 drive, which used the IBM 1316 disk pack to store two million characters.

In 1973, IBM introduced the 3340 “Winchester” disk system, the first to use a sealed head/disk assembly (HDA). Almost all modern disk drives now use this technology, and the term “Winchester” became a common description for all hard disks, though generally falling out of use during the 1990s.

Exhibits in the museum:

• IBM 3336 disk pack, year 1970
• Seagate ST-251, year 198x
• SAMSUNG WN32162U, year 199x