RSSB

RSSB is an esoteric programming language which implements a Turing Complete single instruction computer.

Overview
RSSB stands for Reverse Subtract and Skip if Borrow, taking the principles of RISC to the extreme. The specification defines one instruction, RSSB. Each instruction has one operand, a pointer into memory. There are two registers, IP the instruction pointer, and ACC the accumulator.

The reverse subtract and skip if borrow operation subtracts the accumulator from the contents of memory. The result is stored in both memory and the accumulator. If the result was below zero, the next instruction will be skipped. The instruction pointer is mapped to memory location 0 and the accumulator is mapped to location 1. The complete list of special memory locations is as follows:

Hello, World
This program prints out the words Hello, World!:

; RSSB Hello World, John Metcalf

loop   rssb   acc       ; acc = character from ptr ptr    rssb   hello

rssb  out       ; display character

rssb  zero      ; acc = -acc

rssb  zero      ; always skipped

rssb  sum       ; subtract acc from sum

rssb  ip        ; skipped if sum is <0 ; otherwise jump to 0

rssb  acc       ; subtract 1 from ptr rssb  one rssb  ptr

rssb  acc       ; jump to loop rssb  loopoff rssb  ip loopoff rssb   $-loop

sum    rssb   -1116

one    rssb   1

rssb  33        ; '!' rssb  100       ; 'd'        rssb   108       ; 'l'        rssb   114       ; 'r'        rssb   111       ; 'o'        rssb   87        ; 'W'        rssb   32        ; ' ' rssb  44        ; ',' rssb  111       ; 'o'        rssb   108       ; 'l'        rssb   108       ; 'l'        rssb   101       ; 'e' hello   rssb   72        ; 'H'

External resources

 * An Implementation of RSSB in Redcode
 * Hello World for the RSSB Virtual Computer
 * An RSSB implementation in C