How Does Windows Handle Printers?

Printers come in three flavors:

• Local printers Printers that are physically connected to a USB port of your computer (on older computers, printers can attach to parallel or LPT ports). Typically, a local printer is sitting right next to your computer.

• Network printers Printers that may or may not be in the same room with you, but are connected to the same network as your computer (see Chapter 31).

• Virtual printers Not really printers at all, but they show up as printing options in dialog boxes and as icons in your Printers folder. When you "print" a document to a virtual printer, it doesn't put ink on paper, but it may send a fax or create a file in some compact, widely readable format like Adobe PDF.

Each printer installed on your system has an entry in the Printers folder. When you print something from an application, a Windows printer driver (printer control program) for the current printer formats the material for that particular printer. As far as printer limitations permit, documents look the same no matter what printer they're printed on.

You can have several printers defined on your system. They may be different physical printers or different modes on the same printer. For example, a few printers handle both the Hewlett Packard Printer Control Language (PCL) and the Adobe PostScript language. You can have two printer drivers installed, one for PCL and one for PostScript. If your printer can print on both sides of the paper, you can have two drivers installed, one for single-sided printing and one for double-sided printing. To see the installed printers, open your Printers folder.

At any particular moment, one of the printers is marked as the default printer. Anything you print goes to the default printer unless you specifically tell your program to use a different printer. You can make any of your printers the default by right-clicking its icon in the Printers folder and selecting Set As Default Printer from the shortcut menu.

Windows also provides spooling , a service that stores document data until the printer can accept it. When you print a document from an application, the information to be printed (the print job) is stored temporarily in the queue (storage for print jobs) until it can be printed. If you print a long document to a slow printer, spooling lets you continue working with your application while the printer works in the background. (Many years ago, "spool" stood for Simultaneous Peripheral Operation On-Line, but no one thinks of it as an acronym any more.)