Heath Zenith pioneered the laptop computer market in 1985, with lunchbox portable computer Z 171, the first MS DOS based small portable computer fit with two 514 floppy disks ans blue LCD screen, that was built for Heath Zenith by Vadem Corp. under an OEM agreement, and purchased in large numbers by the US Internal Revenue Service. Next, in 1987, followed the Intel 8088-based Zenith 181 and Zenith 183, the latter being one of the very first laptops to be equipped with a hard disk.