4GL needs to know how many lines of space will be devoted to page headers and trailers; otherwise, it does not know how many detail rows to allow on a page. Since it cannot predict how many lines are in a file, it forbids printing a file in a header or trailer. You can write PRINT statements in the control blocks for FIRST PAGE HEADER, PAGE HEADER, and PAGE TRAILER. However, you cannot write PRINT FILE statements in these control blocks.