DJN (Decrement and jump if not zero) is an OISC. Its instruction
uses Y as a pointer into memory. 1 is subtracted from the value stored at location Y. If the result is non-zero, DJN jumps to X.
DJN is less practical than Subleq type languages since its execution is of O(n) to the values it operates on (exponential to the representation size of the operands).
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