% --- start of displayed preamble in the book --- % --- end of displayed preamble in the book --- defaultfont:="ptmr8r"; warningcheck:=0; beginfig(1) for i=0 upto 5: draw (0,i*6mm)--(3cm,i*6mm); endfor; for i=0 upto 5: draw (i*6mm,0)--(i*6mm,3cm); endfor; endfig; end;