diff --git a/cpu/cpu.c b/cpu/cpu.c
new file mode 100644
index 0000000..a13b59e
--- /dev/null
+++ b/cpu/cpu.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <stdint.h>
+//#define _DEBUG
+int check_registers(int a, int b, int max_reg);
+int main() {
+	int max_reg = 4;
+#ifdef REGISTERS
+	max_reg = REGISTERS;
+#endif
+	/* A, B, C, D. Indice + 5 */
+	uint8_t reg[4] = {0, 0, 0, 0};
+	int i;
+	uint8_t a, b;
+	uint8_t x;
+
+#ifdef _DEBUG
+	printf("%hhu\n", x);
+#endif
+	
+	while (1) {
+		x = getchar() - '0';
+#ifdef _DEBUG
+		printf("x:%hhu\n", x);
+#endif
+		switch (x) {
+			case 0:
+				return 0;
+				break;
+			case 1:
+				scanf("%hhu %hhu\n", &a, &b);
+				if (check_registers(a, b, max_reg)) {
+					printf("-1\n");
+					return 0;
+				}
+				reg[a-5] += reg[b-5];
+				break;
+			case 2:
+				scanf("%hhu %hhu\n", &a, &b);
+				if(check_registers(a, b, max_reg)) {
+					printf("-1\n");
+					return 0;
+				}
+				reg[a-5] -= reg[b-5];
+				break;
+			case 3:
+				scanf("%hhu %hhu\n", &a, &b);
+				if(check_registers(a, 0, max_reg)) {
+					printf("-1\n");
+					return 0;
+				}
+				reg[a-5] = b;
+				break;
+			case 4:
+				for (i = 0; i < max_reg; ++i)
+					printf("%hhu ", reg[i]);
+				putchar('\n');
+				break;
+		}
+	}
+}
+
+int check_registers(int a, int b, int max_reg) {
+	a -= 5;
+	b -= 5;
+	if ((a >= max_reg) || (b >= max_reg))
+		return 1;
+	return 0;
+}