Chapter 12 The Spooler

The Windows NT spooler is the component of the print subsystem that enables print jobs to be routed to local and network printers. It is sometimes referred to as the print subsystem since it is comprised of numerous components. The spooler’s responsibilities include:

• Retrieving the location of the correct printer driver and loading it.

• Accepting a data stream prepared by GDI and/or a printer driver for output on a particular type of printer.

• Ensuring that the driver instructions go to the first available physical printer in a logical printer queue. The spooler supports printing over a network.

• Spooling the data to a file if the printer is not available to print it. If necessary, the spooler converts the high-level function calls to EMFs before storing the print job to disk.

• Delivering data to printers for printing, either directly or by playing back spooled files.

• Providing print-related database management. The spooler maintains a forms database. It also manages a dynamic environment of printers, printer drivers, print providers, monitors, ports, and print jobs. The spooler maintains Registry information from which it can derive how many of these components are in the print subsystem at any time and the unique name of each component. The spooler also keeps track of the current status of each component.

The print spooler is loaded at system startup and continues to run until the operating system is shut down.