diff --git a/main.c b/main.c
index 1e2affc..682cf84 100644
--- a/main.c
+++ b/main.c
@@ -1,5 +1,5 @@
 /*
-    TVM is a LC-3 based virtual machine used for educational purposes
+    TVM is a virtual machine for LC-3 based operating systems and it used for educational purposes.
     Open-source software under MIT License
     Written by Erick Ahmed, 2022
 */
@@ -25,4 +25,24 @@ enum {
     R_COUNT
 };
 
-uint16_t reg[R_COUNT];
\ No newline at end of file
+uint16_t reg[R_COUNT];
+
+/* Creating LC-3 instruction set opcodes */
+enum {
+    OP_BR = 0,      // branch
+    OP_ADD,         // add
+    OP_LD,          // load
+    OP_ST,          // store
+    OP_JSR,         // jump register
+    OP_AND,         // bitwise add
+    OP_LDR,         // load register
+    OP_STR,         // store register
+    OP_RTI,         // unused opcode
+    OP_NOT,         // bitwise not
+    OP_LDI,         // indirect load
+    OP_STI,         // indirect store
+    OP_JMP,         // jump
+    OP_RES,         // reserved opcode
+    OP_LEA,         // load effective address
+    OP_TRAP,        // execute trap
+};