Field of the Invention
The present invention relates to printing apparatuses which print data to be printed (which sometimes will be called print data) received from an external device. 
Description of the Related Art
A system has generally been known which temporarily stores (or reserves) print data transmitted from an external device such as a personal computer in a printing apparatus and prints it in response to a predetermined operation performed by a user on a control panel of the printing apparatus.  Such a system is generally called a reservation printing system. 
In a reservation printing system, a printing apparatus is shared over a network because a user may enter a password on an operation screen and/or a printed product is output in response to a user authentication, for example, and is particularly effective for preventing confidential printed product from being viewed by other people. 
Japanese Patent Laid-Open No.  2000-76028 discloses a system in which a personal computer adds a password to print job and transmits it to a printing apparatus which then prints it in response to an entry of a password matched with the password added to the print job through a control panel of the printing apparatus.