On September 15, 1956, IBM introduced the world's inaugural commercial hard disk drive, dubbed the '350 RAMAC' (an acronym for Random Access Method of Accounting and Control), which was also referred to as the 'Disk Storage Unit' at the time. This groundbreaking device was meticulously crafted for the IBM 305 RAMAC computer system. Its maiden application occurred in June of the same year, when it was integrated into the accounting and inventory control framework of the Zellerbach Paper Company, located in San Francisco.

The 350 RAMAC was a colossal piece of technology, comprising 50 disk platters, each with a diameter of 24 inches. This behemoth weighed in excess of 1 ton and boasted a storage capacity of a mere 3.75MB. Its storage density was a modest 2Kb per square inch, with a rotational speed of 1200RPM and a data transfer rate of 8.8KB/s. At its core, the technology leveraged magnetic storage principles, facilitating data access on the platters via movable read/write heads. These heads hovered approximately 20 micrometers above the platters, employing forced air cushioning technology to achieve seamless random access.

As the world's first commercial hard disk drive, the 350 RAMAC heralded a significant shift from magnetic tape storage to random-access storage, thereby laying the technological groundwork for the evolution of contemporary hard disks.