Nav Computer

A navigation computer, also known as an astrogation computer, navicomputer, navicomp, or nav computer, was a device that made the careful calculations necessary to navigate through hyperspace.
Navicomputers would calculate data like the exact destination, the quickest and safest route to it, and the number of hyperspace jumps necessary. Most starships carried a nav computer of some sort, though some starfighters made do with only the astrogation buffer of an astromech droid. Smaller ships often possessed limited nav computers, capable of containing data for only a small number of jumps; larger ships had large dedicated nav computers capable of storing coordinates for nearly any foreseeable destination. Some nav computers were handheld. Smugglers tended to voice-print their navicomputers to hide where their ship had been.
Although navicomputers were used in most of the known galaxy, they functioned poorly in the Unknown Regions or any area of uncharted space. Navicomputers would also need updates from time to time in case changes had taken place across different routes, such as a new stellar phenomenon blocking passage. 
Traveling with an outdated Navicomputer was very dangerous as there was a chance it may calculate a jump without updated paths of stellar phenomenon, causing the ship to jump straight into whatever object may in the path such as a large asteroid resulting in destruction.
Navicomputers were also responsible for detecting gravitational shadows of objects on the path in an attempt to help avoid jumping through a lone asteroid. Navicomputers would warn the pilots with alarms and some newer models would even force the ship out of Hyperspace in an attempt to avoid destruction.