Abstract: The bit map description for a page printer (1) from data for more lines per page than would normally fit on the page is composed by reserving the full vertical height of one line and determining the line spacing on the basis of the ratio (division) of the remaining printable page length to the number of lines less one. This is done automatically by a microprocessor (7) which determines the lines per page from the page selected from the control panel (13), performs the division (37) of lines per page less one into printable height less one, followed by page composition (39) based on the result. The data invariable fits into the mapped description without additional operator intervention.