OakPDT Drawing

Overview
OakPDT is a 2D parametric CAD system for RISC OS. On RISC OS systems, files in this format typically have a filetype of CAD ("PDT Dwg").

Drawing definition
The drawing definition is an array of opcodes. The return values are pushed in order to a stack, and the parameters are popped in reverse order. Some opcodes have extra data that is read in from the drawing definition and is used as the return value.