[[Image:Hw2-11.gif|right|frame|A "Hello World" program in Piet.]]
'''Piet''' is an [[esoteric programming language]] designed by [[David Morgan-Mar]], whose programs are [[bitmap]]s that look like [[abstract art]]. Piet was named after the Dutch painter [[Piet Mondrian]].
==Computational class==
If the stack is allowed to hold any arbitrarily long number then it's very likely [[Turing-complete]]. There's no formal proof though.
Sketch of a proof for TC: The rotate operation makes every stack position directly accessible, thus making the stack usable as a register bank. It's enough for TC to have two unlimited-size registers and be able to do certain simple operations with them, as stated in the [[Minsky machine]] article. Writing Piet programs is straightforward enough as to make it possible to program the [[finite-state automaton]] needed to simulate an [[universal Turing machine]].
