The initial screen of an infotype is used as a technical interface between transactions within Human Resource Management and the infotype itself. It is accessed via the dialog module assigned to the infotype in question.
Screen
1000 is used as the initial screen for all infotypes. Screen 1000 of module pool MPMMMM00 is used as a model.The initial screen is processed in the background, i.e. the screen is not displayed even though it is processed.
The initial screen performs the following tasks:

You must always create the initial screen using transaction PM01 Enhance Infotypes. The system then creates an initial screen with all of the functions required. Do not change the initial screen.