diff --git a/WinBoyEmulator/GameBoy/CPU/Instruction set/Source.cs b/WinBoyEmulator/GameBoy/CPU/Instruction set/Source.cs
new file mode 100644
index 0000000..a8576a9
--- /dev/null
+++ b/WinBoyEmulator/GameBoy/CPU/Instruction set/Source.cs	
@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace WinBoyEmulator.GameBoy.CPU.Instruction_set
+{
+    /// <summary>
+    /// This class is used to determinite source of opcode <para/>
+    /// Use this with Instruction.Source
+    /// </summary>
+    public static class Source
+    {
+        /// <summary>d8 means immediate 8-bit data.</summary>
+        public const string d8 = "d8";
+
+        /// <summary>d8 means immediate 8-bit data.</summary>
+        public const string d8 = "d8";
+    }
+}
diff --git a/WinBoyEmulator/WinBoyEmulator.csproj b/WinBoyEmulator/WinBoyEmulator.csproj
index c1b0cd0..d85aa34 100644
--- a/WinBoyEmulator/WinBoyEmulator.csproj
+++ b/WinBoyEmulator/WinBoyEmulator.csproj
@@ -54,6 +54,7 @@
     <Compile Include="GameBoy\CPU\Instruction set\Generator\MiscellaneousAndControl.cs" />
     <Compile Include="GameBoy\CPU\Instruction set\IInstruction.cs" />
     <Compile Include="GameBoy\CPU\Instruction set\Instruction.cs" />
+    <Compile Include="GameBoy\CPU\Instruction set\Source.cs" />
     <Compile Include="GameBoy\CPU\IRegisters.cs" />
     <Compile Include="GameBoy\CPU\LR35902.cs" />
     <Compile Include="GameBoy\CPU\Operand.cs" />