1956

Hard Disk

If we review the history of computer storage starting in the 1940s, it is quite a menagerie. Long tubes filled with mercury, giant spinning drums coated in iron oxide, tiny metal donuts handwoven into a cloth of wire … not to mention paper tape, punch cards, and big reels of magnetic tape. Engineers tried just about everything they could think of to store data.

All of those ideas are long obsolete. Except for one that appeared in 1956, developed by IBM for the United States Air Force: the hard disk. Engineers have had a field day making incremental improvements to hard disks for more than half a century and the results have been spectacular.

The first hard disks were as big as refrigerators and incredibly expensive. They stored just a few million characters. However, the fundamental concepts were identical to those used today. A rigid aluminum disk spins on a shaft. The coating on the disk records magnetic changes. A read/write head on an arm can move to different tracks on the disk. To keep from wearing out the head and the magnetic coating, the read/write head flies on an air cushion above the disk.

Engineers have improved everything since then. The coating on the disk allows denser and denser recording. The head gets smaller to take advantage of the density. The arm gets more precise and faster. Where engineers once stored thousands of bits per square inch of disk surface, they now store millions. But the biggest difference is cost. It once cost $15,000 to store one million bytes. Now it costs tiny fractions of a penny.

This incremental cost-lowering and improvement process is one of the hallmarks of engineering. They start with an initial idea and improve it over time. The Wright brothers get a plane in the air, and a few decades later, people are inexpensively flying from America to Europe at Mach 0.8. Engineers start with expensive, bulky radio phones and a few decades later we have inexpensive smart phones in our pockets. Initially a computer fills a room and costs millions. A few decades later we buy laptops a million times more powerful for a few hundred dollars. It is one of the best things about engineering.

SEE ALSO The Wright Brothers’ Airplane (1903), ENIAC—The First Digital Computer (1946), Smart Phone (2007).

A tiny read/write head floats above the disk’s surface when the disk is spinning. The lightweight aluminum arm pictured here holds the head and moves it to different tracks on the disk.