diff --git a/src/core/FunctionValue.cs b/src/core/FunctionValue.cs
index 4b9d991..418dd29 100644
--- a/src/core/FunctionValue.cs
+++ b/src/core/FunctionValue.cs
@@ -9,7 +9,22 @@ namespace csmic
 {
     public class FunctionValue
     {
-        public required csmic.ValueType Type { get; set; }
+        public ValueType Type { get; set; }
         public object? Value { get; set; }
+
+        public static readonly FunctionValue TRUE = new FunctionValue(ValueType.Numeric, 1);
+        public static readonly FunctionValue FALSE = new FunctionValue(ValueType.Numeric, 0);
+
+        public FunctionValue()
+        {
+            this.Type = ValueType.None;
+            this.Value = null;
+        }
+
+        public FunctionValue(ValueType type, object? value)
+        {
+            this.Type = type;
+            this.Value = value;
+        }
     }
 }
diff --git a/src/core/ICodedFunction.cs b/src/core/ICodedFunction.cs
index 140ce6a..4baf142 100644
--- a/src/core/ICodedFunction.cs
+++ b/src/core/ICodedFunction.cs
@@ -11,6 +11,7 @@ namespace csmic
         #region Properties
 
         IEnumerable<FunctionArgument> ExpectedArguments { get; }
+        FunctionValue ReturnValue { get; }
 
         #endregion
 
diff --git a/src/core/InputInterpreter.cs b/src/core/InputInterpreter.cs
index 3d0ca37..cae5446 100644
--- a/src/core/InputInterpreter.cs
+++ b/src/core/InputInterpreter.cs
@@ -1,7 +1,69 @@
-namespace csmic
+using System.Runtime.CompilerServices;
+
+namespace csmic
 {
     public class InputInterpreter
     {
+        #region Members
 
+        private decimal numericValue = 0;
+        private string stringValue = string.Empty;
+
+        #endregion
+
+        #region Properties
+
+        public decimal NumericValue
+        {
+            get
+            {
+                return numericValue;
+            }
+        }
+
+        public string StringValue
+        {
+            get
+            {
+                return stringValue;
+            }
+        }
+
+        #endregion
+
+        #region Methods
+
+        internal void ProduceOutput(decimal numericValue, string stringValue)
+        {
+            this.numericValue = numericValue;
+            this.stringValue = stringValue;
+        }
+
+        internal void ProduceOutput(FunctionValue functionValue)
+        {
+            switch (functionValue.Type)
+            {
+                case ValueType.Numeric:
+                    decimal numericValue = Convert.ToDecimal(functionValue.Value);
+                    ProduceOutput(numericValue, string.Empty);
+                    break;
+                case ValueType.String:
+                    if (functionValue.Value != null && functionValue.Value is string)
+                    {
+                        ProduceOutput(0, functionValue.Value!.ToString());
+                    }
+                    else
+                    {
+                        ProduceOutput(0, string.Empty);
+                    }
+                    break;
+                case ValueType.None:
+                default:
+                    ProduceOutput(0, string.Empty);
+                    break;
+            }
+        }
+
+        #endregion
     }
 }
diff --git a/src/core/Variable.cs b/src/core/Variable.cs
new file mode 100644
index 0000000..166d4fb
--- /dev/null
+++ b/src/core/Variable.cs
@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace cs_mic.core
+{
+    public class Variable
+    {
+        #region Members
+
+        private VariableType type;
+
+        private string name;
+
+        private object value;
+
+        #endregion
+
+        #region Constructor
+
+        public Variable()
+        {
+            this.type = VariableType.None;
+            this.value = string.Empty;
+        }
+
+        #endregion
+    }
+}
diff --git a/src/core/VariableType.cs b/src/core/VariableType.cs
new file mode 100644
index 0000000..2c4bc76
--- /dev/null
+++ b/src/core/VariableType.cs
@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace cs_mic.core
+{
+    public enum VariableType
+    {
+        None,
+        Numeric,
+        NumericArray,
+        String,
+        StringArray,
+        Expression,
+    }
+}
diff --git a/src/core/cocor/Interpreter.atg b/src/core/cocor/Interpreter.atg
index 6a2ea0f..6932af5 100644
--- a/src/core/cocor/Interpreter.atg
+++ b/src/core/cocor/Interpreter.atg
@@ -10,30 +10,17 @@ COMPILER INTERPRETER
 *
 */
 
-private decimal calcValue = 0;
-private string stringValue = string.Empty;
+private FunctionValue value = new FunctionValue();
 
 public decimal CalculatedValue
 {
 	get
 	{
-		return this.calcValue;
+		return this.value;
 	}
 	set
 	{
-		this.calcValue = value;
-	}
-}
-
-public string StringValue
-{
-	get
-	{
-		return this.stringValue
-	}
-	set
-	{
-		this.stringValue = value
+		this.value = value;
 	}
 }
 
@@ -126,8 +113,7 @@ IGNORE cr + tab
  PRODUCTIONS
 
  INTERPRETER								(.
-												decimal decimalValue = 0;
-												string stringValue = string.Empty;
+												FunctionValue functionValue = new FunctionValue();
 												bool success = true;
 												if(this.interpreter == null)
 												{
@@ -137,7 +123,7 @@ IGNORE cr + tab
 =
 
 	IF(IsCompare())
-	Comparison<out success>					(. this.calcValue = (success == true) ? 1 : 0; .)
+	Comparison<out success>					(. this.functionValue = (success == true) ? FunctionValue.TRUE : FunctionValue.FALSE; .)
 	|
 	IF(IsAssignment())
 	Assignment<out r>
\ No newline at end of file