diff --git a/cpu.c b/cpu.c
index 1345d8b..4b55818 100644
--- a/cpu.c
+++ b/cpu.c
@@ -35,29 +35,7 @@
 #define PULL()	\
 	(peek(0x0100 + ++regs.sp))
 
-struct cpu_flags {
-	uint8_t carry : 1;
-	uint8_t zero : 1;
-	uint8_t interrupt_disable : 1;
-	uint8_t decimal_mode : 1;
-	uint8_t brk : 1;
-	uint8_t unused : 1;
-	uint8_t overflow : 1;
-	uint8_t negative : 1;
-};
-
-struct registers {
-	uint8_t a, x, y, sp;
-	struct cpu_flags status;
-	uint16_t pc;
-};
-struct registers regs = {0};
-
 struct Rom rom = {0};
-
-/* 64K address space, 16bit words */
-uint8_t memory[0x16000];
-
 uint32_t cycles = 0;
 
 bool page_crossed = false;
@@ -72,6 +50,8 @@ peek(uint16_t addr)
 			return rom.prg_rom[(addr - 0x8000) % 0x4000];
 		else if (rom.prg_rom_size == 0x8000)
 			return rom.prg_rom[addr - 0x8000];
+		else
+			fprintf(stderr, "PRG ROG size is not 0x4000 nor 0x8000\n"), exit(1);
 	} else {
 		return memory[addr];
 	}
@@ -953,7 +933,6 @@ interpret(void)
 			page_crossed = false;
 		}
 	}
-loop_exit:
 }
 
 /* https://www.nesdev.org/wiki/CPU_power_up_state */
diff --git a/cpu.h b/cpu.h
index ed17432..05c30fa 100644
--- a/cpu.h
+++ b/cpu.h
@@ -1,5 +1,29 @@
+#ifndef CPU_H
+#define CPU_H
+
 #include <stdint.h>
 
+struct cpu_flags {
+	uint8_t carry : 1;
+	uint8_t zero : 1;
+	uint8_t interrupt_disable : 1;
+	uint8_t decimal_mode : 1;
+	uint8_t brk : 1;
+	uint8_t unused : 1;
+	uint8_t overflow : 1;
+	uint8_t negative : 1;
+};
+
+struct registers {
+	uint8_t a, x, y, sp;
+	struct cpu_flags status;
+	uint16_t pc;
+};
+struct registers regs = {0};
+
+/* 64K address space, 16bit words */
+uint8_t memory[0x16000];
+
 /* OFFICIAL OPCODES */
 void ADC(uint16_t arg);
 void AND(uint16_t arg);
@@ -87,3 +111,5 @@ void SYA(uint16_t arg);
 void TOP(uint16_t arg);
 void XAA(uint16_t arg);
 void XAS(uint16_t arg);
+
+#endif	/* CPU_H */