User:Lar/ToDo/Cliff Biffle
(removed AfD message as this got userified, in prep for turning it into a bio article on the author (with possible merge targets of the other langs he did)
4DL is an esoteric programming language written by Cliff Biffle. It is similar to Befunge, but with instructions arranged on a four-dimensional grid, rather than Befunge's two-dimensional page.
Execution follows the journey of an instruction pointer, which has a particular trajectory within the program space. Instructions are capable of deflecting the instruction pointer in one direction or another, or cause it to skip subsequent instructions before proceeding.
Visualization of 4DL programs is difficult, but the website helps.
Some extensions to 4DL, such as subroutines or multiple data stacks.