The NULL programming language is an esoteric programming language designed to be zero-dimensional. Its design was inspired by the two-dimensional Befunge language to contrast with conventional one-dimensional programming languages. A NULL program consists of a single arbitrarily large positive integer.

An interpreter for the language manages three queues of bytes and two integer variables x and y. Initially x is set to the program-integer, y to 1 and the queues to 0, 1 and 2. The instruction set consists of all the prime numbers, however, every 14th prime number corresponds to the same instruction:

 2  Select the next queue (2 loops to 0).
 3  Select the previous queue (0 loops to 2).
 5  Output the character whose ascii value is the same as the
    byte at the front of the selected queue.  
 7  Input one character, then replace the byte at
    the front of the selected queue with its ascii value.
11  Subtract the byte at the front of the selected queue from y.
    If this would reduce y to less than 0, then y=0 instead.
13  Add the byte at the front of the selected queue to y.
17  Add y to the byte at the front of the selected queue.
19  Move the byte at the front of the selected queue to the rear
    of the next queue (2 loops to 0).
23  Move the byte at the front of the selected queue to the rear
    of the previous queue (0 loops to 2).
29  Dequeue the selected queue.
31  Enqueue y to the selected queue.
37  If the selected queue is empty or the front byte has a value of
    0, divide x by its smallest prime factor and multiply y by that number.
41  Switch the values of x and y.
43  End the program.

A program is executed as follows: the value in x is divided by its smallest prime factor, y is multiplied by that prime factor, and the instruction corresponding to it is executed. This process is repeated until the "End the program" instruction is executed or until x is 0 or 1.

External links

• NULL language specification
• source code for NULL interpreter in Python by Kang Seonghoon