diff --git a/asm_files/01-01-37.asm b/asm_files/01-01-37.asm
index d7361c1..723f3e9 100644
--- a/asm_files/01-01-37.asm
+++ b/asm_files/01-01-37.asm
@@ -4,4 +4,4 @@
 
 bits 16
 
-mov bx, cx                      ; mov 001, 011
+mov cx, bx                      ; mov 001, 011
diff --git a/decode.c b/decode.c
index c25cfb1..f190adc 100644
--- a/decode.c
+++ b/decode.c
@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include "lib.h"
 
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
 
@@ -8,22 +9,6 @@ enum Instruction
     INST_MOV = 0b10001000
 };
 
-enum Register
-{
-    REG_AL_AX = 0b000,
-    REG_CL_CX = 0b001,
-    REG_DL_DX = 0b010,
-    REG_BL_BX = 0b011,
-    REG_AH_SP = 0b100,
-    REG_CH_BP = 0b101,
-    REG_DH_SI = 0b110,
-    REG_BH_DI = 0b111,
-};
-
-#define REG_AX "ax"
-#define REG_CX "cx"
-#define REG_BX "bx"
-
 enum Mode
 {
     MODE_MEM_NOD = 0b00,
@@ -32,6 +17,31 @@ enum Mode
     MODE_REGMODE = 0b11,
 };
 
+typedef struct Register
+{
+    char code;
+    char *fullname;
+    char *bytename;
+    union {
+        struct {
+            char low;
+            char high;
+        };
+        u16 full;
+    } value;
+} Register;
+
+Register registers[8] = {
+    {.code = 0b000, .fullname = "ax", .bytename = "al" },
+    {.code = 0b001, .fullname = "cx", .bytename = "cl" },
+    {.code = 0b010, .fullname = "dx", .bytename = "dl" },
+    {.code = 0b011, .fullname = "bx", .bytename = "bl" },
+    {.code = 0b100, .fullname = "sp", .bytename = "ah" },
+    {.code = 0b101, .fullname = "bp", .bytename = "ch" },
+    {.code = 0b110, .fullname = "si", .bytename = "dh" },
+    {.code = 0b111, .fullname = "di", .bytename = "bh" },
+};
+
 int main(int argc, char **argv)
 {
     if (argc < 2)
@@ -52,42 +62,23 @@ int main(int argc, char **argv)
     printf("bits 16\n\n");
     for (int i = 0; i < (int)bytes_read / 2; i += 2)
     {
-        char byte = buf[i];
-        switch (byte & 0b11111100)
+        char low_byte = buf[i];
+        char high_byte = buf[i+1];
+        // char w = byte & 0b00000001;
+        char d = low_byte & 0b00000010;
+        char mod = (high_byte & 0b11000000) >> 6;
+        char reg = (high_byte & 0b00111000) >> 3;
+        char r_m = (high_byte & 0b00000111);
+        size_t reg_idx = reg;
+        size_t r_m_idx = r_m;
+        Register src_reg = d == 0 ? registers[reg_idx] : registers[r_m_idx];
+        Register dst_reg = d == 0 ? registers[r_m_idx] : registers[reg_idx];
+        switch (low_byte & 0b11111100)
         {
         case INST_MOV:
-            char high_byte = buf[i+1];
-            // char w = byte & 0b00000001;
-            // char d = byte & 0b00000010;
-            char mod = (high_byte & 0b11000000) >> 6;
-            char reg = (high_byte & 0b00111000) >> 3;
-            char r_m = (high_byte & 0b00000111);
-            printf("mov ");
             if (mod == MODE_REGMODE)
             {
-                char *dest_reg_name = NULL;
-                switch (r_m)
-                {
-                case REG_CL_CX:
-                    dest_reg_name = REG_CX;
-                    break;
-                case REG_BL_BX:
-                    dest_reg_name = REG_BX;
-                    break;
-                }
-                printf("%s, ", dest_reg_name);
-                
-                char *src_reg_name = NULL;
-                switch (reg)
-                {
-                case REG_CL_CX:
-                    src_reg_name = REG_CX;
-                    break;
-                case REG_BL_BX:
-                    src_reg_name = REG_BX;
-                    break;
-                }
-                printf("%s", src_reg_name);
+                printf("mov %s, %s", dst_reg.fullname, src_reg.fullname);
             }
             break;
         default:
diff --git a/lib.h b/lib.h
new file mode 100644
index 0000000..bebd135
--- /dev/null
+++ b/lib.h
@@ -0,0 +1,26 @@
+#pragma once
+#include <stdint.h>
+#include <stddef.h>
+
+typedef uint8_t   u8;
+typedef uint16_t  u16;
+typedef int16_t   i16;
+typedef int32_t   i32;
+typedef uint32_t  u32;
+typedef uint64_t  u64;
+typedef float     f32;
+typedef double    f64;
+typedef uintptr_t uptr;
+typedef char      sbyte;
+typedef ptrdiff_t size;
+typedef size_t    usize;
+
+#define OPTION(type, typeName)                  \
+    struct {                                    \
+        enum {NONE, SOME} tag;                  \
+        union {                                 \
+            u8 none;                            \
+            type typeName;                      \
+        } some;                                 \
+    }
+