Parallel port the ports in this manner in many cases, though this is often fairly hidden. In SCO UNIX and Linux, the first parallel port is available via the filesystem as /dev/lp0. Linux IDE devices can use a "paride" (parallel port IDE) driver. For consumers, USB and computer networks have replaced the parallel printer port, for connections both to printers and to other devices. Many manufacturers of personal computers and laptops consider parallel to be a legacy port and no longer include the parallel interface. Smaller machines have less room for large parallel port connectors. USB-to-parallel adapters are available that can make
Parallel manipulator others, rather than being cumulative. Each actuator must still move within its own degree of freedom, as for a serial robot; however in the parallel robot the off-axis flexibility of a joint is also constrained by the effect of the other chains. It is this closed-loop stiffness that makes the overall parallel manipulator stiff relative to its components, unlike the serial chain that becomes progressively less rigid with more components. This mutual stiffening also permits simple construction: Stewart platform hexapods chains use prismatic joint linear actuators between any-axis universal ball joints. The ball joints are passive: simply free to move,