4 ms·It's stated in the FAQ: Was PDOS written in C90? As a matter of fact, yes. PDOS was in fact written in C90.by anta40 4y agoIt's stated in the FAQ: Was PDOS written in C90? As a matter of fact, yes. PDOS was in fact written in C90.rkta 4y agoYes, it's the only topic of the FAQ, hence the smiley.signaru 4y agoCurious question. How hard would it be to write an OS in Turtle Graphics?