1The IDEAL program puts out a code that is intended to be device-independent. 2It looks like TROFF comments so that IDEAL output may be NROFFed safely, 3or it may be filtered to produce TROFF commands to draw the picture. 4It may also be run through filters that throw away all text but what 5appears between .IS and .IE, in which case only the pictures in the 6document will be run through the plot filter. 7 8Elements of the output: 9 10.IS 11 start a picture; 12 13...minx x 14 x becomes the logical x-coordinate of the upper left corner 15...maxy y 16 y becomes the logical y-coordinate of the upper left corner 17...maxx x 18 x becomes the logical x-coordinate of the lower right corner 19...miny y 20 y becomes the logical y-coordinate of the lower right corner 21...width w 22 scale the picture to be w inches wide 23...colwid w 24 center the picture in a column w inches wide 25...line x1 y1 x2 y2 26 draw a line segment from (x1,y1) to (x2,y2) 27...circle x0 y0 r 28 draw a circle of radius r centered at (x0,y0) 29...arc x0 y0 x1 y1 x2 y2 theta1 theta2 r 30 draw a counterclockwise arc of radius r centered at (x0,y0), 31 starting at (x1,y1), at an angle theta1, 32 ending at (x2,y2), at an angle theta2 33...spline x0 y0 x1 y1 x2 y2 ... 34 draw a spline through the points named 35...left x0 y0 'string 36 write string so it starts at (x0,y0) 37...center x0 y0 'string 38 write string so it is centered at (x0,y0) 39...right x0 y0 'string 40 write string so it ends at (x0,y0) 41.IE 42 end picture 43.IF 44 end picture 45