It appears to be an svg. It could have been drawn using any number of tools, or by hand: svg is remarkably understandable. In this case, it was drawn with Inksc

It appears to be an svg. It could have been drawn using any number of tools, or by hand: svg is remarkably understandable. In this case, it was drawn with Inkscape: view source on http://sarabander.github.io/sicp/html/fig/chap1/Fig1.5d.std.svg http://sarabander.github.io/sicp/html/fig/chap1/Fig1.5d.std....