As far as your application is concerned, a printer is a printer is a printer. For the most part, the exact details of each printer don’t matter. All output is arranged and printed a page at one time. Your program generates a page of output, and it is sent to the Print Manager to hold in a temporary file. This file is also known as a spool file.
The Print Manager continues to hold your output until you use either the EndDoc method or the KillDoc method. The EndDoc method tells the Print Manager to release the spool file and begin printing it. The KillDoc method tells the Print Manager to delete the spool file immediately, before it is sent to the printer.