USB It has largely replaced interfaces such as serial ports and parallel ports, and has become commonplace on a wide range of devices. USB connectors have been increasingly replacing other types for battery chargers of portable devices. This section is intended to allow fast identification of USB receptacles (sockets) on equipment. Further diagrams and discussion of plugs and receptacles can be found in USB (Physical) § Connectors. The Universal Serial Bus was developed to simplify and improve the interface between personal computers and peripheral devices, when compared with previously existing standard or ad-hoc proprietary interfaces. From the computer user's perspective, the
Eagle Computer of the clamshell was the reset button, two RS-232 serial ports labeled "Serial A" and "Serial B", a Centronics parallel port labeled "Parallel A", a SASI port labeled "Parallel B", the brightness knob for the monitor, and the on/off switch. The keyboard was well-designed. The keys were black with white lettering. Besides a full typewriter keyboard, there was a complete ten-key number pad on the right, uncommon at that time. Labels on the "front" of the number keys of the typewriter keyboard, and all the keys of the number pad, denoted what function those keys performed in the command mode