diff --git a/src/global.h b/src/global.h
index e827bcb..138e11a 100644
--- a/src/global.h
+++ b/src/global.h
@@ -5,8 +5,8 @@
  ********************************************************************************
  */
 
-#ifndef GLOBAL_H
-#define GLOBAL_H
+#ifndef __GLOBAL__
+#define __GLOBAL__
 #include <stdint.h>
 
 // Number of General Purpose Registers.
@@ -18,7 +18,11 @@
 // Length of the instruction in bits.
 #define INSTRUCTION_SIZE 32
 
-// Define the word type to be a 64-bit unsigned integer.
-typedef uint64_t word;
+// A byte is an 8-bit unsigned integer in this architecture.
+typedef uint8_t byte;
+// A word is a 32-bit unsigned integer in this architecture.
+typedef uint32_t word;
+// Double word is a 64-bit unsigned integer.
+typedef uint64_t dword;
 
 #endif
\ No newline at end of file