diff --git a/SDA.c b/SDA.c
index ff50bd2..2ea0509 100644
--- a/SDA.c
+++ b/SDA.c
@@ -4,17 +4,17 @@
 #ifndef SDA
 #define SDA
 #include <stdio.h>
-
+#include "stackslot.c"
 struct sda {
     int *size;
-    unsigned int *sda;
+    ObjRef *sda;
 };
 
-unsigned int getSDA(int i, struct sda s) {
+ObjRef getSDA(int i, struct sda s) {
     return s.sda[i];
 }
 
-void setSDA(int point, int val, struct sda s) {
+void setSDA(int point, ObjRef val, struct sda s) {
     s.sda[point] = val;
 }
 
diff --git a/consts.c b/consts.c
index 348d59a..f9e447a 100644
--- a/consts.c
+++ b/consts.c
@@ -1,6 +1,6 @@
 #ifndef CONSTS
 #define CONSTS
-#define VERSION 8
+#define VERSION 5
 
 #endif /* ifndef CONSTS
 #define CONSTS
diff --git a/nja/nja5 b/nja/nja5
index 1e6a1ce..67ee60f 100755
Binary files a/nja/nja5 and b/nja/nja5 differ
diff --git a/njvm.c b/njvm.c
index 70902b1..51b9bab 100644
--- a/njvm.c
+++ b/njvm.c
@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include "instruktion.c"
 #include "code.c"
@@ -6,16 +7,17 @@
 #include "program.c"
 #include "codeReader.c"
 #include "SDA.c"
+#include "reg.c"
 
 // Debug
-int debug = 0;
+int debug = 1;
 
 // Stack
 struct stack stack;
 #define SIZE 1000
 
 //Register
-struct stack reg;
+struct reg reg;
 
 // Program
 struct program program;
@@ -37,73 +39,74 @@ void execute(struct program program) {
     int intInput;
     unsigned int temp;
     char charInput;
+    StackSlot tempSlot;
     for (i = 0; i < *program.size; ++i) {
         if (debug == 1) printf("=== DEBUG: Stack before instruction %i ===\n", i);
         if (debug == 1) printStack(stack, fp);
         if (debug == 1) printf("=== DEBUG: Instruction %i ===\n", i);
-
+        
         switch (program.program[i] >> 24) {
             case HALT:
                 if (debug == 1) printf("halt\n");
                 goto end;
             case PUSHC:
                 if (debug == 1) printf("pushc: %i\n", IMMEDIATE(program.program[i]));
-                push(stack, SIGN_EXTEND(IMMEDIATE(program.program[i])));
+                push(stack, stackSlotWithObjRef(getIntObj(SIGN_EXTEND(IMMEDIATE(program.program[i])))));
                 break;
             case ADD:
-                if (debug == 1) printf("add: %i + %i\n", peek(stack, 2), peek(stack, 1));
-                push(stack, pop(stack) + pop(stack));
+                if (debug == 1) printf("add: %i + %i\n", * (int *)peek(stack, 2).u.objRef->data, * (int *)peek(stack, 1).u.objRef); 
+                push(stack, stackSlotWithObjRef(getIntObj(getIntValfromStackSlot(pop(stack)) + getIntValfromStackSlot(pop(stack)))));
                 break;
             case SUB:
                 if (debug == 1) printf("sub: %i - %i\n", peek(stack, 2), peek(stack, 1));
-                temp = pop(stack);
-                push(stack, pop(stack) - temp);
+                temp = getIntValfromStackSlot(pop(stack));
+                push(stack, stackSlotWithObjRef(getIntObj(getIntValfromStackSlot(pop(stack)) - temp)));
                 break;
             case MUL:
                 if (debug == 1) printf("mul: %i * %i\n", peek(stack, 2), peek(stack, 1));
-                push(stack, pop(stack) * pop(stack));
+                push(stack, stackSlotWithObjRef(getIntObj(getIntValfromStackSlot(pop(stack)) * getIntValfromStackSlot(pop(stack)))));
                 break;
             case DIV:
                 if (debug == 1) printf("div: %i / %i\n", peek(stack, 2), peek(stack, 1));
-                temp = pop(stack);
-                push(stack, pop(stack) / temp);
+                temp = getIntValfromStackSlot(pop(stack));
+                push(stack, stackSlotWithObjRef(getIntObj(getIntValfromStackSlot(pop(stack)) / temp)));
                 break;
             case MOD:
                 if (debug == 1) printf("mod: %i %% %i\n", peek(stack, 2), peek(stack, 1));
-                temp = pop(stack);
-                push(stack, pop(stack) % temp);
+                temp = getIntValfromStackSlot(pop(stack));
+                push(stack, stackSlotWithObjRef(getIntObj(getIntValfromStackSlot(pop(stack)))));
                 break;
             case RDINT:
                 if (debug == 1) printf("rdint\n");
                 scanf("%i", &intInput);
-                push(stack, intInput);
+                push(stack, stackSlotWithObjRef(getIntObj(intInput)));
                 if (debug == 1) printf("pushed %i\n", intInput);
                 break;
             case WRINT:
                 if (debug == 1) printf("wrint: %i\n", peek(stack, 1));
-                printf("%i", pop(stack));
+                printf("%i", getIntValfromStackSlot(pop(stack)));
                 break;
             case RDCHR:
                 if (debug == 1) printf("rdchr\n");
                 scanf("%c", &charInput);
-                push(stack, charInput);
+                push(stack, stackSlotWithObjRef(getIntObj(charInput)));
                 if (debug == 1) printf("pushed %c\n", charInput);
                 break;
             case WRCHR:
                 if (debug == 1) printf("wrchr: %c\n", peek(stack, 1));
-                printf("%c", pop(stack));
+                printf("%c", getIntValfromStackSlot(pop(stack)));
                 break;
             case PUSHG:
                 if (debug == 1) printf("pushg: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
-                push(stack, getSDA(SIGN_EXTEND(IMMEDIATE(program.program[i])), sda));
+                push(stack, stackSlotWithObjRef(getSDA(SIGN_EXTEND(IMMEDIATE(program.program[i])), sda)));
                 break;
             case POPG:
                 if (debug == 1) printf("popg: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
-                setSDA(SIGN_EXTEND(IMMEDIATE(program.program[i])), pop(stack), sda);
+                setSDA(SIGN_EXTEND(IMMEDIATE(program.program[i])), pop(stack).u.objRef, sda);
                 break;
             case ASF:
                 if (debug == 1) printf("asf: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
-                push(stack, fp);
+                push(stack, stackSlotWitchNumber(fp));
                 fp = *stack.current;
                 *stack.current = *stack.current + SIGN_EXTEND(IMMEDIATE(program.program[i]));
                 break;
@@ -111,7 +114,8 @@ void execute(struct program program) {
                 if (debug == 1) printf("rsf: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
                 *stack.current = fp;
                 if (debug == 1) printf("pop: %i\n", peek(stack, 1));
-                fp = pop(stack);
+                tempSlot = pop(stack) ;
+                fp = getIntValfromStackSlot(tempSlot);
                 break;
             case POPL:
                 if (debug == 1) printf("popl: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
@@ -123,42 +127,42 @@ void execute(struct program program) {
                 break;
             case NE:
                 if (debug == 1) printf("ne: %i != %i\n", peek(stack, 2), peek(stack, 1));
-                if (pop(stack) != pop(stack)) push(stack, 1);
-                else push(stack, 0);
+                if (getIntValfromStackSlot(pop(stack)) != getIntValfromStackSlot(pop(stack))) push(stack, stackSlotWitchNumber(1));
+                else push(stack, stackSlotWitchNumber(0));
                 break;
             case EQ:
                 if (debug == 1) printf("eq: %i == %i\n", peek(stack, 2), peek(stack, 1));
-                if (pop(stack) == pop(stack)) push(stack, 1);
-                else push(stack, 0);
+                if (getIntValfromStackSlot(pop(stack)) == getIntValfromStackSlot(pop(stack))) push(stack, stackSlotWitchNumber(1));
+                else push(stack, stackSlotWitchNumber(0));
                 break;
             case LT:
                 if (debug == 1) printf("lt: %i < %i\n", peek(stack, 2), peek(stack, 1));
-                temp = pop(stack);
-                if (pop(stack) < temp) push(stack, 1);
-                else push(stack, 0);
+                temp = getIntValfromStackSlot(pop(stack));
+                if (getIntValfromStackSlot(pop(stack)) < temp) push(stack, stackSlotWitchNumber(1));
+                else push(stack, stackSlotWitchNumber(0));
                 break;
             case LE:
                 if (debug == 1) printf("le: %i <= %i\n", peek(stack, 2), peek(stack, 1));
-                temp = pop(stack);
-                if (pop(stack) <= temp) push(stack, 1);
-                else push(stack, 0);
+                temp = getIntValfromStackSlot(pop(stack));
+                if (getIntValfromStackSlot(pop(stack)) <= temp) push(stack, stackSlotWitchNumber(1));
+                else push(stack, stackSlotWitchNumber(0));
                 break;
             case GT:
                 if (debug == 1) printf("gt: %i > %i\n", peek(stack, 2), peek(stack, 1));
-                temp = pop(stack);
-                if (pop(stack) > temp) push(stack, 1);
-                else push(stack, 0);
+                temp = getIntValfromStackSlot(pop(stack));
+                if (getIntValfromStackSlot(pop(stack)) > temp) push(stack, stackSlotWitchNumber(1));
+                else push(stack, stackSlotWitchNumber(0));
                 break;
             case GE:
                 if (debug == 1) printf("ge: %i >= %i\n", peek(stack, 2), peek(stack, 1));
-                temp = pop(stack);
-                if (pop(stack) >= temp) push(stack, 1);
-                else push(stack, 0);
+                temp = getIntValfromStackSlot(pop(stack));
+                if (getIntValfromStackSlot(pop(stack)) >= temp) push(stack, stackSlotWitchNumber(1));
+                else push(stack, stackSlotWitchNumber(0));
                 break;
             case BRF:
                 if (debug == 1) printf("brf: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
                 if (debug == 1) printf("pop: %i\n", peek(stack, 1));
-                if (pop(stack) == 0) {
+                if (getIntValfromStackSlot(pop(stack)) == 0) {
                     i = SIGN_EXTEND(IMMEDIATE(program.program[i])) - 1;
                     if (debug == 1) printf("new i: %i\n", i);
                 }
@@ -166,7 +170,7 @@ void execute(struct program program) {
             case BRT:
                 if (debug == 1) printf("brt: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
                 if (debug == 1) printf("pop: %i\n", peek(stack, 1));
-                if (pop(stack) == 1) {
+                if (getIntValfromStackSlot(pop(stack)) == 1) {
                     i = SIGN_EXTEND(IMMEDIATE(program.program[i])) - 1;
                     if (debug == 1) printf("new i: %i\n", i);
                 }
@@ -178,7 +182,7 @@ void execute(struct program program) {
                 break;
             case CALL:
                 if (debug == 1) printf("call: %i\n", SIGN_EXTEND(IMMEDIATE(program.program[i])));
-                push(stack, i);
+                push(stack, stackSlotWitchNumber(i));
                 if (debug == 1) printf("push: %i\n", i + 1);
                 i = SIGN_EXTEND(IMMEDIATE(program.program[i])) - 1;
                 if (debug == 1) printf("new i: %i\n", i);
@@ -186,23 +190,23 @@ void execute(struct program program) {
             case RET:
                 if (debug == 1) printf("ret\n");
                 if (debug == 1) printf("pop: %i\n", peek(stack, 1));
-                i = pop(stack);
+                i = getIntValfromStackSlot(pop(stack));
                 if (debug == 1) printf("new i: %i\n", i);
                 break;
             case DROP:
                 *stack.current = *stack.current - SIGN_EXTEND(IMMEDIATE(program.program[i]));
                 break;
             case DUP:
-                temp = pop(stack);
-                push(stack, temp);
-                push(stack, temp);
+                temp = getIntValfromStackSlot(pop(stack));
+                push(stack, stackSlotWitchNumber(temp));
+                push(stack, stackSlotWitchNumber(temp));
                 break;
             case PUSHR:
                 //TODO
-                push(reg, SIGN_EXTEND(IMMEDIATE(program.program[i])));
+                pushR(reg, SIGN_EXTEND(IMMEDIATE(program.program[i])));
                 break;
             case POPR:
-                push(stack, pop(reg));  
+                push(stack, stackSlotWitchNumber(popR(reg)));  
                 break;
       
         }
@@ -275,7 +279,7 @@ int main(int argc, char *argv[]) {
 
     if (run) {
         printf("Ninja Virtual Machine started\n");
-        unsigned int s[sizeSDA];
+        ObjRef s[sizeSDA];
         sda.size = &sizeSDA;
         sda.sda = s;
         if (debug == 1) printProgram(program);
diff --git a/programs/prog04.asm b/programs/prog04.asm
new file mode 100644
index 0000000..a1fec33
--- /dev/null
+++ b/programs/prog04.asm
@@ -0,0 +1,32 @@
+//
+// prog04.asm -- call/ret with args, and with ret value
+//
+
+	asf	3
+	pushc	11
+	wrint
+	pushc	'\n'
+	wrchr
+	pushc	11
+	pushc	33
+	call	proc
+	drop	2
+	pushr
+	wrint
+	pushc	'\n'
+	wrchr
+	pushc	33
+	wrint
+	pushc	'\n'
+	wrchr
+	rsf
+	halt
+
+proc:
+	asf	2
+	pushl	-3
+	pushl	-4
+	sub
+	popr
+	rsf
+	ret
diff --git a/reg.c b/reg.c
new file mode 100755
index 0000000..65b3ce5
--- /dev/null
+++ b/reg.c
@@ -0,0 +1,49 @@
+//
+// Created by Nils on 29.10.2023.
+//
+#ifndef REG
+#define REG
+
+#include <stdio.h>
+#include <stdlib.h>
+
+struct reg {
+    int* size;
+    int* current;
+    unsigned int *stack;
+};
+
+void printStackR(struct reg stack, int fp) {
+    printf("Stack\nSize:\t\t%i\nCurrent:\t%i\n", *stack.size, *stack.current);
+    for (int i = 0; i < *stack.current; ++i) {
+        if(fp == i) printf("|FP|\n");
+        printf("|%i|\n", stack.stack[i]);
+    }
+}
+
+void pushR(struct reg s, unsigned int value) {
+    if (*s.current >= *s.size) {
+        printf("Stack Overflow\n");
+        exit(EXIT_FAILURE);
+    }
+    s.stack[*s.current] = value;
+    *s.current=*s.current + 1;
+}
+
+unsigned int popR(struct reg s) {
+    if (*s.current == 0) {
+        printf("Stack Underflow\n");
+        exit(EXIT_FAILURE);
+    }
+    *s.current = *s.current -1;
+    return s.stack[*s.current];
+}
+
+unsigned int peekR(struct reg s, int steps) {
+    if (*s.current - steps < 0) {
+        printf("Stack Underflow\n");
+        exit(EXIT_FAILURE);
+    }
+    return s.stack[*s.current - steps];
+}
+#endif
diff --git a/stack.c b/stack.c
index 10feff0..f481085 100755
--- a/stack.c
+++ b/stack.c
@@ -6,11 +6,12 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include "stackslot.c"
 
 struct stack {
     int* size;
     int* current;
-    unsigned int *stack;
+    StackSlot *stack;
 };
 
 void printStack(struct stack stack, int fp) {
@@ -21,7 +22,7 @@ void printStack(struct stack stack, int fp) {
     }
 }
 
-void push(struct stack s, unsigned int value) {
+void push(struct stack s, StackSlot value) {
     if (*s.current >= *s.size) {
         printf("Stack Overflow\n");
         exit(EXIT_FAILURE);
@@ -30,7 +31,7 @@ void push(struct stack s, unsigned int value) {
     *s.current=*s.current + 1;
 }
 
-unsigned int pop(struct stack s) {
+StackSlot pop(struct stack s) {
     if (*s.current == 0) {
         printf("Stack Underflow\n");
         exit(EXIT_FAILURE);
@@ -39,7 +40,7 @@ unsigned int pop(struct stack s) {
     return s.stack[*s.current];
 }
 
-unsigned int peek(struct stack s, int steps) {
+StackSlot peek(struct stack s, int steps) {
     if (*s.current - steps < 0) {
         printf("Stack Underflow\n");
         exit(EXIT_FAILURE);
diff --git a/stackslot.c b/stackslot.c
new file mode 100644
index 0000000..5cbd04a
--- /dev/null
+++ b/stackslot.c
@@ -0,0 +1,55 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifndef STACKSLOT
+#define STACKSLOT
+typedef int Object;
+typedef struct {
+  unsigned int size;
+  unsigned char data[1];
+} *ObjRef;
+
+typedef struct{
+  bool isObjRef;
+  union {
+    ObjRef objRef;
+    int number;
+  } u;
+} StackSlot;
+
+ObjRef getIntObj(int val){
+  ObjRef intObject;
+  unsigned int objSize = sizeof(unsigned int) + sizeof(int);
+  if ((intObject = malloc(objSize)) == NULL) {
+    perror("malloc");
+  }
+  *(int *)intObject->data=val;
+  return intObject;
+}
+int getValFromIntObj(ObjRef iref){
+  return *(int *)iref->data;
+}
+int getIntValfromStackSlot(StackSlot s){
+  if(s.isObjRef){
+    return *(int *)s.u.objRef->data;
+  }
+  return s.u.number;
+}
+void setValIntObj(ObjRef iref, int val){
+  *(int *)iref->data=val;
+}
+StackSlot stackSlotWithObjRef(ObjRef val){
+  StackSlot *stackSlot;
+  stackSlot=malloc(sizeof(StackSlot));
+  stackSlot->isObjRef=true;
+  stackSlot->u.objRef=val;
+  return *stackSlot;
+}
+StackSlot stackSlotWitchNumber(int val){
+  StackSlot *stackSlot;
+  stackSlot= malloc(sizeof(StackSlot));
+  stackSlot->isObjRef=false;
+  stackSlot->u.number=val;
+  return *stackSlot;
+}
+#endif
diff --git a/test.bin b/test.bin
new file mode 100644
index 0000000..9a783d0
Binary files /dev/null and b/test.bin differ