If you are looking for detailed information about CGM, see the NIST CGM Homepage. This is my "cgm hotlist".
CGM Draw is a freely available library for generating CGM files from a C program. It has been tested on Solaris, Ultrix, Linux, IRIX, and DOS. CGM (Computer Graphics Metafile) is a vector graphics format that can be read by many popular packages. With CGM Draw your code can quickly draw images complete with lines, arcs, rectangles, polygons, and text. CGM Draw is ideal for creating CGM files on the fly when you have a rapidly changing data set (such as in response to database queries.)