IBM 350 RAMAC The RAMAC (Random Access Method of Accounting and Control) was

announced in 1956. It included the first rotating magnetic disk drive for mass data storage. It was the first storage device to provide direct access in less than a second to 5 million characters. This capacity and the short access time capability it provided marked the beginning of a revolution in computing by introducing real-time transaction processing and replacing the sequential data processing procedures required with data stored on punched cards or magnetic tape. Features The RAMAC’s disk drive consisted of a stack of 50 magnetic disks that were 2 feet in diameter. This disk drive could store 5 million characters using a 6-bit character code plus a parity and space bit per character. The characters were organized into 50,000 100-character records. The maximum access time was 0.8 seconds to any record in the disk stack, which rotated at 1,200 rpm. Data was recorded on each disk side in circumferential tracks. The RAMAC disk drive introduced several radically new innovations to devices for magnetic digital data recording. Those innovations in storing digital data included the following. • 1. A stack of closely spaced magnetic disks rotating at high speed. • 2. An access mechanism for positioning two read/write heads to tracks, one for each side of a disk, and for inserting and withdrawing the heads to move up and down the stack to quickly access any specific disk track. • 3. A pressurized air-bearing head (which required compressed air) to maintain a small non-contact spacing. • 4. A miniature read/write head to fit within the small spacing between the disks that included a wide erase head to deal with positioning tolerances. • 5. The development of spin coating to achieve a uniform coating of magnetic iron oxide paint on the aluminum dis