One exception to proprietary barcode label printers is a thermal barcode label printer based on the Hewlett Packard printer command language (HP PCL). In 1990 HP introduced the LaserJet III, which featured HP PCL5 and included GL/2, the control language that provides vector graphics su
pport. PCL5 with GL/2 supports fonts of any spacing, scale and design including mono-spaced and proportionally scaled fonts, rotated, scalable, filled/shadowed/mirrored, as well as downloaded predesigned forms and overlays. The flexibility of PCL5 revolutionized the word processing market. The success of PCL5 vaulted Hewlett Packard to the leadership position in laser printing and established PCL as the de facto industry standard printing language. Today HP PCL is the most widely-used printer command language in the world.
The OpenPrinting workgroup maintains the Linux ljtet3 driver for the LaserJet III. The ljet3 driver is a CUPS (Common Unix Printing System) GhostScript driver that is certified to work perfectly (a three penguin highest ranking) with all current versions of major Linux distributions. The ljet3 driver also works perfectly with a thermal printer based on PLC5 with a LaserJet III emulation.