diff --git a/SLS_C/include/sls/interpreter.h b/SLS_C/include/sls/interpreter.h
index 8a8b3d6..a07a79a 100644
--- a/SLS_C/include/sls/interpreter.h
+++ b/SLS_C/include/sls/interpreter.h
@@ -8,6 +8,8 @@
 
 #include <stddef.h>
 
+#include "sls/lexer.h"
+
 typedef enum {
     STACK_IDENTIFIER,
     STACK_I64,
@@ -23,9 +25,35 @@ typedef enum {
     STACK_CHARACTER,
     STACK_BOOLEAN,
     STACK_TOKEN_STRING,
-} StackTypes;
+} StackType;
 
 extern const char *STACK_TYPES_NAMES[];
 extern const size_t STACK_TYPE_COUNT;
 
+typedef struct StackItem {
+    StackType type;
+    union {
+        Identifier identifier;
+        int64_t i64;
+        int32_t i32;
+        int16_t i16;
+        int8_t i8;
+        uint64_t u64;
+        uint32_t u32;
+        uint16_t u16;
+        uint8_t u8;
+        float f32;
+        double f64;
+        char character;
+        Boolean boolean;
+        TokenString token_string;
+    };
+    StackItem *next;
+} StackItem;
+
+typedef struct {
+    StackItem *stack;
+    
+} InterpreterState;
+
 #endif // SLS_INTERPRETER_H