The datajack was invented in the 2491 by a Sivadian by the name of Dylan Phelps to allow hackers and other computer elite to quickly and efficiently interface the humanoid brain with 95% of computer technology, allowing the user to 'jack' themselves into systems via a simple computer cord and run commands using only thoughts. It wasn't until 2512 that the datajack was available to Shohobian races, and in 2526, limited download capability was introduced.
Installation of a datajack requires minor surgery, as a wire has to be interfaced with the brain itself. A translation microcomputer is inserted into the user's skull just below the ear region, and a small cluster of wires pass under the bottom of the brainpan, ending in a datajack port. Usually this port is built flush with the user's skin just below the ear, but this can be altered to port out at either the temple or via some part of the ear. It is much less invasive than the later model, the Neurojack.
Datajacks are required for the use of several kinds of technology in the modern world, including some kinds of powered armor, See-alls, a handful of fightercraft, and a variety of others.