bf.c

#include <stdio.h>
#include <stdlib.h>

typedef enum {
	MOV,
	SET,
	ADD,
	SUB,
	JMP,
	SYSCALL,
	EXIT
} keyword;


typedef enum {
	GET,
	PUT
} syscalls;

typedef struct {
	keyword opcode;
	int arg1;
	int arg2;
} instruction;

int main(void) {
	int *registers = malloc(16 * sizeof(char));
	instruction bytecode[] = {
		{ SET, 0, 0 },
		{ SET, 3, 1 },
		{ SYSCALL, GET, 1 },
		{ SYSCALL, PUT, 1 },
		{ JMP, 1, 0 },
	};

	size_t pc = 0;
	while (1) {
		int a1 = bytecode[pc].arg1;
		int a2 = bytecode[pc].arg2;
		int *r1 = registers + a1;
		int *r2 = registers + a2;
		switch(bytecode[pc].opcode) {
			case MOV:
				*r1 = *r2;  ++pc; break;
			case SET:
				*r2 = a1;   ++pc; break;
			case ADD:
				*r2 += *r1; ++pc; break;
			case SUB:
				*r2 -= *r1; ++pc; break;
			case JMP:
				if (!*r2)     pc = *r1;
				else        ++pc; break;
			case SYSCALL:
				switch(a1) {
					case PUT: putchar(*r2);      break;
				        case GET: (*r2) = getchar(); break;
				}
				            ++pc; break;
			default:
				return a1;
		}
	}
}