A printer driver is software used by computer programs to communicate with printers and plotters. Printer drivers translate the information you send from the computer into commands that the printer understands. Usually, printer drivers are not compatible across platforms, so various drivers must be installed on the print server to support different hardware and operating systems. For example, if you are running Windows XP and you share a printer with users running Windows 3.1, you might need to install multiple printer drivers.
In general, printer drivers are made up of three types of files:
Configuration or printer interface file
Displays the Properties and Preferences dialog boxes when you configure a printer. This file has a .dll extension.
Provides information about the capabilities of a specific printer, including its resolution capability, whether it can print on both sides of the page, and what size paper it can accept. This file could have a .dll, .pcd, .gpd, or .ppd extension.
Printer graphics driver file
Translates device driver interface (DDI) commands into commands that a printer can understand. Each driver translates a different printer language. For example, the file Pscript.dll translates the PostScript printer language. This file has a .dll extension.
These files, which are usually accompanied by a Help file, work together to make printing possible. For example, when you install a new printer, the configuration file reads the data file and displays the available printer options. When you print, the graphics driver file queries the configuration file about your selections so that it can create the proper printer commands.