One of the few mistakes I found is on page 700, where the snippet (apparently accidentally copied from the documentation of fill on page 589):
gsave
fill
grestore
should be replaced by: gsave
stroke
grestore
PostScript allows very concise and elegant programs, ideal to visualize information in readable and scalable ways.Also check out Display Postscript for inspiration:
https://en.wikipedia.org/wiki/Display_PostScript
Rest in peace Charles Geschke, and thank you and your colleagues for PostScript!