PURPOSE: To simplify the process of paper replacing operation, by stopping printing operation at the point of time when data printing justly performed until the terminal of a page even when a residual paper reduced state is detected during printing.

CONSTITUTION: A data processing apparatus 1 issues a control code C1 for indicating usual data transfer demand and the succeeding of printing/new line control to a printing apparatus 3 regardless of a residual paper reduced state at the initial stage in issuing a slip. On the other hand, the data processing apparatus 1 checks a paper state and determines the transfer possibility of next page data but, because delay is present in a paper state signal 22, issues a control code C2 for indicating the next data transfer demand to the printing apparatus 3 after all printing/new line operations of data remaining in buffer memory 322-2 are finished. Thereafter, the data processing apparatus 1 checks the paper state after waits the reception of the data transfer demand and transfers the slip data of the next page when the paper is present but performs the display of the residual paper reduced state without transferring the slip data of the next page if the paper residual is small.