NULL

NULL is a programming language in zero dimensions. Programs in it are single positive integers of arbitrarily large size.

Runtime environment
The environment available to a NULL program consists of three queues of bytes, initially empty, and two arbitrarily large integer variables, x and y. x is set to the program, while y is set to 1.

Then x is divided by its smallest prime factor, y is multiplied by the same, and the instruction corresponding to the prime factor is executed.

Instructions
The instructions loop for every 14th prime number, meaning, for instance, 47 is equivalent to 2.

Hello, world!
This 199-digit number prints the words Hello, world!.

50056520978563208516819797718881283032143646116073595166114838703987562227081772 27277884468665934749909633552472002670467760272184148189288786549011066838407636 978909259289001144030816758344442315793

Cat program
This 5-digit number is a cat program. Note that its behaviour on end of file is undefined. 42539

External resources

 * NULL website
 * NULL interpreter in Python, with mirror in the Esoteric File Archive
 * NULL interpreter in Rust