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EXOTIC STORAGE
Glossary of PC terms: P
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| Parity | A data-checking technique, which uses an extra bit. If you send one extra-bit for each 8 bits to make sure your data got there intact, add and send one more bit - a parity bit. Bit parity could be odd or even. If it is even, you assign 0 to the parity bit in case when the sum of 8 bits is a even number and 1 if it is odd. If it is odd, the logic is reversed. After the byte has arrived, the system will sum 8 bits and check if it matches the eve-or-oddness predicted by the parity byte. |
| Partition | Procedure dividing a physical hard drive into into one or more logical volumes. |
| Parallel port | Also called a printer port. A 25-pin port that sends 8 bits of data in parallel. For details go here. |
| Particulate media | A magnetic media design consisting of a mixture of iron oxide magnetic particles and a polymer matrix. Presently, it is used in the floppy disks, magnetic tapes, and other magnetic storage systems that do not require extremely high areal density. See also Thin film disk. |
| PC card | A small form-factor memory card used with mobile computers, handheld, sub-notebook, desktop personal computers, industrial controllers, laser printers, and other devices. Formerly known as PCMCIA card. |
| PCMCIA card (Personal Computer Memory Card International Association) | See PC card. |
| PFA (Predictive Failure Analysis) | Technology meant to increase drive reliability by automatically warning a user of approaching drive failures. It monitors key device performance indicators, including head-to-disk flying height, and reports when specific levels and thresholds are exceeded. See SMART. |
| Physical Vapor Deposition (PVD) | A process of thin film formation via transporting atoms evaporated from one surface onto another surface. Evaporation occurs due to surface heating or bombardment by high-energy ions in vacuum. The film composition replicates the target composition, unless it is additionally doped with other materials. |
| Pits | Holes on the surface of the optical storage media. Pits are the coded data and carry the information. See also Lands. |
| Photodetector | A solid-state electronic device that converts light intensity into electric current. |
| Platter | A rigid disk in a hard disk drive. Most drives use more than one platter. Each platter typically requires two magnetic read/write elements - one for each side. |
| PIO(Processor Input / Output) | A means of data transfer requiring the use of the CPU. |
| PRML (Partial Responce Maximum Likelihood) | A type of digital read channel designed for higher recording density and data transfer rates. Partial Response is a sampling procedure used to detect signals so that inter-symbol interference is reduced and the signal-to-noise ratio is enhanced. Maximum Likelihood technique analyzes the read signal and constructs the data stream with statistically smallest error. |
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