3. When were they initially made?

The first ever production hard drive, was by IBM , called the "IBM 305 RAMAC (Random Access Method of Accounting and Control), introduced on September 13, 1956"[7]. It boasted 50 cylinders, approximately 24" in diameter (compared to the 3.5" drives of today), and was able to boast a transfer rate of "an impressive 8,800 bytes per second"[2,7].

"Over the succeeding years, the technology improved incrementally; areal density, capacity and performance all increased. In 1962, IBM introduced the model 1301 Advanced Disk File. The key advance of this disk drive was the creation of heads that floated, or flew, above the surface of the disk on an "air bearing", reducing the distance from the heads to the surface of the disks from 800 to 250 microinches."[7]

"In 1973, IBM introduced the model 3340 disk drive, which is commonly considered to be the father of the modern hard disk."[7], This had 2 cylinders, each of 30MB capacity, one fixed and another removable. "Using the first sealed internal environment and vastly improved "air bearing" technology, the Winchester disk drive greatly reduced the flying height of the disk to only 17 microinches above the surface" of the cylinders.[7]

"The first hard disk drive designed in the 5.25" form factor used in the first PCs was the Seagate ST-506. It featured four heads and a 5 MB capacity. IBM bypassed the ST-506 and chose the ST-412--a 10 MB disk in the same form factor--for the IBM PC/XT", this was then the first widely used hard drive in the modern PC, and PC compatible machine.[2,7]

Today one hard drive can hold 300 GB or more. They can be measures for capacity, average seek time, and the data transfer rate.[3,7]

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Gregg Williams, 294805, CS_134 Web Report