diff --git a/kernel/syscall/skeleton.cc b/kernel/syscall/skeleton.cc
index 6d8eed4..a424383 100644
--- a/kernel/syscall/skeleton.cc
+++ b/kernel/syscall/skeleton.cc
@@ -14,7 +14,6 @@ void *operator new(size_t, void *);
 
 uint8_t mapNumber = 0;
 
-uint32_t next_start_v = 0x4000;
 
 namespace Syscall {
   namespace Skeleton {
@@ -163,6 +162,7 @@ namespace Syscall {
     void* getFreeVirtSpace(four_lvl_paging_t* search_table, uint8_t num_pages){
       uint32_t start_v = 0x4000;
       uint32_t stop_v = 0x6000;
+      static uint32_t next_start_v = 0x4000;
       //static uint32_t next_start_v = start_v;
 
       //start from last found address
@@ -174,7 +174,7 @@ namespace Syscall {
               }
           }
           if(space_is_free){
-              next_start_v = v+num_pages;
+              //next_start_v = v+num_pages;
               return  (void*) ((uintptr_t) (v <<12));
           }
       }
@@ -202,6 +202,7 @@ namespace Syscall {
 
         if(!(flpt->l4->entries[l4Index].present)){
             pagetable_t* newl3 = (pagetable_t*)PageFrameAllocator::alloc(true);
+            memset(newl3, 0, 4096);
             flpt->l4->entries[l4Index] = {
                 .present = 1,
                 .write = 1,
@@ -213,6 +214,7 @@ namespace Syscall {
         pagetable_t* lvl3 = (pagetable_t*)(flpt->l4->entries[l4Index].address<<12);
         if(!(lvl3->entries[l3Index].present)){
             pagetable_t* newl2 = (pagetable_t*)PageFrameAllocator::alloc(true);
+            memset(newl2, 0, 4096);
             lvl3->entries[l3Index] = {
                 .present = 1,
                 .write = 1,
@@ -224,6 +226,7 @@ namespace Syscall {
         pagetable_t* lvl2 = (pagetable_t*)(lvl3->entries[l3Index].address<<12);
         if(!(lvl2->entries[l2Index].present)){
             pagetable_t* newl1 = (pagetable_t*)PageFrameAllocator::alloc(true);
+            memset(newl1, 0, 4096);
             lvl2->entries[l2Index] = {
                 .present = 1,
                 .write = 1,
@@ -233,15 +236,16 @@ namespace Syscall {
         }
 
         pagetable_t* lvl1 = (pagetable_t*)(lvl2->entries[l2Index].address<<12);
-        assert(!(lvl1->entries[l1Index].present)); // should not be present, bc its a new mapping
 
-        if(frame)
+        if(frame){
+            assert(!(lvl1->entries[l1Index].present)); // should not be present, bc its a new mapping
             lvl1->entries[l1Index] = {
                 .present = 1,
                 .write = 1,
                 .user = 1,
                 .address = (uintptr_t)frame >> 12
             };
+        }
         else //unmap if nullptr
             lvl1->entries[l1Index].present = 0;
     }
diff --git a/kernel/thread/thread.cc b/kernel/thread/thread.cc
index 098325b..61f5e35 100644
--- a/kernel/thread/thread.cc
+++ b/kernel/thread/thread.cc
@@ -38,8 +38,14 @@ Thread::Thread 	(bool kernel, void * startframe, int num_pages): queue_link(null
 	StackPointer.user = (void*)(0x61FF000+STACK_SIZE);
 
 	paging_tree = (four_lvl_paging_t*)PageFrameAllocator::alloc(true);
+	memset(paging_tree, 0, 4096);
 	create_basic_page_table(paging_tree, &identity_table);
+
 	appcode_table = (pagetable_t*) PageFrameAllocator::alloc(true);
+	memset(appcode_table, 0, 4096);
+
+	appstack_table = (pagetable_t*) PageFrameAllocator::alloc(true);
+	memset(appstack_table, 0, 4096);
 
 	assert(num_pages < 512); //limit for application code size is 2M
 	for(uint8_t i=0; i<num_pages; i++){
diff --git a/user/app1/appl.cc b/user/app1/appl.cc
index 9a9aef3..6049f15 100644
--- a/user/app1/appl.cc
+++ b/user/app1/appl.cc
@@ -1,6 +1,44 @@
 // vim: set noet ts=4 sw=4:
 
 #include "../libsys/stub.h"
+#include "../libsys/string.h"
+
+char* itoh(unsigned int value, char* buffer) {
+    char* ptr = &buffer[11];
+    *ptr = '\0'; // Nullterminator am Ende setzen
+
+    if (value == 0) {
+        *--ptr = '0';
+        return ptr;
+    }
+
+    do {
+        ptr--;
+        *ptr = '0' + (value % 16);
+		if(*ptr >= 0x3A)
+			*ptr+=7;
+        value /= 16;
+    } while (value != 0);
+
+    return ptr;
+}
+char* itoa(unsigned int value, char* buffer) {
+    char* ptr = &buffer[11];
+    *ptr = '\0'; // Nullterminator am Ende setzen
+
+    if (value == 0) {
+        *--ptr = '0';
+        return ptr;
+    }
+
+    do {
+        ptr--;
+        *ptr = '0' + (value % 10);
+        value /= 10;
+    } while (value != 0);
+
+    return ptr;
+}
 
 extern "C" void main() {
 	// Thread 1 may be an auxiliary thread
@@ -10,31 +48,29 @@ extern "C" void main() {
 	unsigned id = sys_getpid();
 	char text[] = "appX";
 	text[3] = 0x30+id;
-	char buf = 32;
 
 	write(1, text, sizeof(text), 0, (int)id);
 
 	uint8_t cnt = 0;
 	for (unsigned i = 1;; ++i) {
-		char msg[5];
-		msg[0] = 0x30+cnt;
-		msg[1] = 0;
-		cnt=(cnt+1)%10;
-		write(1, msg, 1, 6, (int)id);
-		void* ptr= map(512);
 
-		//sprintf(&buf, "ptr address: %x \n" , ptr);
-		//unmap(ptr, 512);
+		//counter to see app running
+		cnt=(cnt+1)%100;
+		char buf[12];
+		char* msg = itoa(cnt,buf);
+		write(1, msg, strlen(msg), 6, (int)id);
 
+		// test map/unmap and print ptr
+		void* ptr= map(4096);
+		uint16_t* val = ((uint16_t*)ptr);
+		*val = 0x1337;
 
-		//if(i==id){
-		//	//write(2, "kill", 4);
-		//	//write(2, &text[4], 1);
-		//	//write(2, " ", 1);
-		//	sys_exit();
-		//}
-		sleep(1000);
-		if(id == 2)
+		msg = itoh((uintptr_t)ptr,buf);
+		write(1, msg, strlen(msg), 12, (int)id);
+		unmap(ptr, 4096);
+
+		sleep(100);
+		if(id == 4)
 			*reinterpret_cast<uint8_t*>(0xdeadbeaf) = 1;
 	}
 }