A computer assembly having a host computer and a detachably attached computer expansion module. The computer expansion module includes a 2D imaging module, and may include short range imaging optics. In a "picture taking" mode actuated by input into the host computer, the expansion module captures an image, and without launching a decoding algorithm, sends the captured image to the host computer which displays the image on an integrated display of the host computer. In a "decode" mode actuated by input to the host computer, the expansion module captures an image, executes a decoding algorithm, and sends a decoded out message to the host computer, which displays the decoded out message on an integrated display of the host computer.