Rule 110 simulation in a single variable/register. This approach can be used for hardware implementations, using a long shift register and a minimal number of logic gates.

110.c

#include <stdint.h>
#include <stdio.h>

void main(void) {
    register uint32_t line = 0b10;
    for (int i = 0; i < 31; i++) {
        for (int j = 0; j < 31; j++) {
            putchar(((line & 0b100) >> 2) * ('#' - ' ') + ' ');
            uint8_t cond = line & 0b111;
            line >>= 1;
            if (cond != 0b111 && cond != 0b001 && cond != 0b000) {
                line = line | ((uint32_t)1 << 31);
            }
        }
        putchar('\n');
    }
}