It built small custom fragments of code. But if that had been in D space, it couldn't have been executed. Exactly. That is the essence of stored-program computers. The exec system call is self-modification with a vengeance. Fill memory-and-execute is the grandest coercion I know. What is data one instant is code the next. It's all a matter of viewpoint and scale. Where is the boundary between changing one instruction and changing them all? Or is this boundary a figment of imagination? Doug