It describes a page being printed by sending commands that describe the text as well as the margins and other settings. The printer controller in the printer interprets these commands and turns them accordingly. The first page-description language was PostScript, developed by Adobe and used in the Apple LaserWriter printer. Another page-description language is the Printer Control Language (PCL and currently PCL 6, was developed by Hewlett-Packard for its laser printers. It made printing graphics fast and simple.
Working – PostScript printer driver describes the page in terms of “draw” and “position” commands. The page is divided into a grid so, to print a square, the command will be like
POSITION 2, 24%DRAW 20%POSITION 2, 34%DRAW20D% . . .
This command draws a line on a specific page by giving the starting and ending points, rather location of each and every dot in the line. PostScript can draw with fewer instructions. The commands are interpreted by the printer’s controller and converted into the print-control signals.