Parallel interface

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A parallel interface (or parallel port) is a hardware port which uses many physical conductors in parallel (hence the name) through which data can be transferred into and out of a computer. Use of a parallel port is generally simpler, and less likely to cause a problem if an error is made, than going directly to the machine's basic underlying bus.

The voltages, means of signalling when a new group of data are available, etc will vary from one machine (and interface) to another. For many years, personal computers (especially IBM-compatible PCs) did include standardized parallel ports; they were most commonly used for attaching printers, but a vast array of different devices used them: tape drives for backups, scanners, etc.

These have now generally been replaced with serial interfaces such as USB ports, as the synchronization of signals coming across independent lines can be problematic, especially at higher speeds. Also, in general, the long-term trend has been to accept use of more logic, to allow sharing of conductors; so, for example, a single serial input is fed into a shift register, to convert the data back to a parallel form.