8

8 is an esoteric programming language made by User:AmNow.

Commands

8 runs in an infinite loop, until it hits the 0 command. (see below)

1:[x]: = Print X. Replace the colons with semicolons if you don’t want a newline.
2:[x]<[y]: = Set X to the value of Y.
3:[x]: = Gets variable X’s value.
4:[x]: = Input Into Variable X.
5:[x];(y): = While X is true, Do Y.
6:[x]’[op]’[y]: = Do X OP Y and store the result in X. Replace the apostrophes with commas to return the value and not store in a variable 
7:[x]§(y): = Like 5, but do it once.
0:: = Halt Execution.

Programs

Hello, World!

1:[“Hello, World!”]:
0::

Truth Machine

4:[inp]:
1;[3:[inp]:];
5:[6:[3:[inp]:],[==],[1]:](
    1;[1];
):
0::

Computational Class

8 is (obviously) Turing Complete.