diff --git a/src/isr.c b/src/isr.c
index e3ea96c..64a9311 100644
--- a/src/isr.c
+++ b/src/isr.c
@@ -4,6 +4,7 @@
 #include "pic_controler.h"
 #include "debug.h"
 #include "syscall.h"
+#include "userland.h"
 
 void isr_default_int(void)
 {
@@ -17,7 +18,15 @@ void isr_page_fault(void)
 
 void isr_clock_int(void)
 {
-    DEBUG_INFO("Enterring clock interrupt handler.");
+    DEBUG_INFO("Clock interrupt handler.");
+    for (int i = (userland_data->curent_process + 1) % 128; i != userland_data->curent_process; i = (i + 1) % 128)
+    {
+        if (userland_data->active_process[i / 32] & (1 << (i % 32)))
+        {
+            switch_to_process(i);
+            return;
+        }
+    }
 }
 
 void isr_kbd_int(void)
diff --git a/src/kernel.c b/src/kernel.c
index e31e104..4125271 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -22,8 +22,12 @@ void main(void)
     char *data_end       = _binary_a_out_end;
     size_t data_size  = (size_t)_binary_a_out_size;
 
+	u16 tss = 0x28;
+
 	create_process(0, data_start);
-	switch_to_process(0);
+	create_process(1, data_start);
+	userland_data->active_process[0] |= 1 << (1 % 32);
+	switch_to_ring_3(0);
 
 	for (;;)
 	{
diff --git a/src/launch_process.c b/src/launch_process.c
index 18ca823..fe3869b 100644
--- a/src/launch_process.c
+++ b/src/launch_process.c
@@ -2,32 +2,33 @@
 
 #include "tss.h"
 #include "debug.h"
+#include "userland.h"
 
-void launch_process(u16 tss, int memory_start, int userland_stack, int userland_code, u16 userland_data)
+void launch_process(u16 tss, int memory_start, int userland_stack, int userland_code, u16 userland_data_seg)
 {
     // Setting DPL and GDT bits
     userland_stack += 3;
     userland_code += 3;
-    userland_data += 3;
+    userland_data_seg += 3;
 
     DEBUG_INFO("LAUCHING USER LAND PROCESS");
 
-    asm volatile ("             \n \
-        mov %0, %%ax            \n \
-        ltr %%ax                \n \
-        movw %%ss, %1           \n \
-        movl %%esp, %2          \n \
-        movw $0x23, %%ax            \n \
-        movw %%ax, %%ds         \n \
-        movw %%ax, %%es         \n \
-        movw %%ax, %%fs         \n \
-        movw %%ax, %%gs         \n \
-        mov %%esp, %%eax         \n \
-        push $0x23                 \n \
-        push $0x7FFFEFFF         \n \
-        pushfl                  \n \
-        push $0x1B                 \n \
-        push $0x6000000         \n \
+    asm volatile ("         \n \
+        mov %0, %%ax	    \n \
+        ltr %%ax            \n \
+        movw %%ss, %1       \n \
+        movl %%esp, %2      \n \
+        movw $0x23, %%ax    \n \
+        movw %%ax, %%ds     \n \
+        movw %%ax, %%es     \n \
+        movw %%ax, %%fs     \n \
+        movw %%ax, %%gs     \n \
+        mov %%esp, %%eax    \n \
+        push $0x23          \n \
+        push $0x7FFFEFFF    \n \
+        pushfl              \n \
+        push $0x1B          \n \
+        push $0x6000000     \n \
         iret" : "+r" (tss),
                 "=m" (user_land_tss.ss0),
                 "=m" (user_land_tss.esp0));
diff --git a/src/pic_controler.c b/src/pic_controler.c
index 92f27ad..3c9911e 100644
--- a/src/pic_controler.c
+++ b/src/pic_controler.c
@@ -101,6 +101,8 @@ void pic_init(void)
         IRQ_set_mask(i);
     }
 
+    DEBUG_INFO("Unmasking IRQ 0 - Clock");
+    IRQ_clear_mask(0);
     DEBUG_INFO("Unmasking IRQ 1 - Keyboard");
     IRQ_clear_mask(1);
     
diff --git a/src/userland.c b/src/userland.c
index e154f90..44f5afc 100644
--- a/src/userland.c
+++ b/src/userland.c
@@ -30,6 +30,21 @@ int create_process(int uid, char *data_start)
     return 0;
 }
 
+int switch_to_ring_3(int uid){
+    DEBUG_INFO("SWITCHING TO RING 3");
+    void *process_page_dir_adress = userland_data->userland_data[uid].page_directories;
+
+    // load cr3
+    asm volatile ("                 \
+        mov %0, %%eax     \n \
+        mov %%eax, %%cr3" : "+r" (process_page_dir_adress));
+
+    userland_data->curent_process = uid;
+    userland_data->active_process[uid / 32] |= 1 << (uid % 32);
+
+    launch_process(0x28, 0x6000000, 0x20, 0x18, 0x20);
+}
+
 int switch_to_process(int uid)
 {
     DEBUG_INFO("SWITCHING TO PROCESS");
@@ -40,6 +55,8 @@ int switch_to_process(int uid)
         mov %0, %%eax     \n \
         mov %%eax, %%cr3" : "+r" (process_page_dir_adress));
 
-    // TODO : once data by process has been implemented, load the right one
-    launch_process(0x28, 0x6000000, 0x20, 0x18, 0x20);
+    userland_data->curent_process = uid;
+    userland_data->active_process[uid / 32] |= 1 << (uid % 32);
+
+    return 0;
 }
diff --git a/src/userland.h b/src/userland.h
index c89a721..3ebdb84 100644
--- a/src/userland.h
+++ b/src/userland.h
@@ -10,17 +10,19 @@ struct userland_data
 {
     struct page_directory_entry page_directories[1024];
     struct page_table_entry page_table[1024];
-};
+} __attribute__((packed));
 
 
 struct userlands_data {
     struct userland_data userland_data[128];
-    u32 page_dir[4];
-};
+    int curent_process;
+    u32 active_process[4];
+} __attribute__((packed));
 
 extern struct userlands_data *userland_data;
 
 int create_process(int uid, char *data_start);
+int switch_to_ring_3(int uid);
 int switch_to_process(int uid);
 
 #endif /*   !USERLAND_H */