diff --git a/include/instructions.h b/include/instructions.h
index e9e6ef2..08ce355 100644
--- a/include/instructions.h
+++ b/include/instructions.h
@@ -13,9 +13,13 @@ public:
   uint32_t eflags;              // EFLAGS register
   uint32_t eip;                 // Instruction pointer
 
+  uint8_t modrm, mod, R, M;     // ModRM
+
   void (Instructions::*instructions[256])(void);
 
   void init(uint32_t eip, uint32_t esp, Memory memory);
+  void init_modrm();
+  void calc_modrm();
   void execute_opcode(uint8_t opcode);
 
   void nop();
diff --git a/instructions.cpp b/instructions.cpp
index e360bdd..ee73a52 100644
--- a/instructions.cpp
+++ b/instructions.cpp
@@ -14,6 +14,7 @@ void Instructions::init(uint32_t eip, uint32_t esp, Memory memory){
   this->memory = memory;
 
   this->init_instructions();
+  this->init_modrm();
 }
 
 void Instructions::init_instructions(){
@@ -23,6 +24,19 @@ void Instructions::init_instructions(){
   this->instructions[0xf4] = &Instructions::hlt;
 }
 
+void Instructions::init_modrm(){
+  this->modrm = 0;
+  this->mod   = 0;
+  this->R     = 0;
+  this->M     = 0;
+}
+
+void Instructions::calc_modrm(){
+  this->mod = (this->modrm & 0xc0) >> 6;
+  this->R   = (this->modrm & 0x38) >> 3;
+  this->M   =  this->modrm & 0x07;  
+}
+
 void Instructions::execute_opcode(uint8_t opcode){
   (this->*instructions[opcode])();
 }