diff --git a/Makefile b/Makefile
index f3a9fb5..525510e 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@ KERNEL = deados.bin
 ISO = deados.iso
 
 SOURCES_C = kernel.c tty.c idt.c timer.c io.c vga.c gdt.c sys.c irq.c isr.c keyboard.c shell.c string.c user_space.c syscall.c
-SOURCES_ASM = boot.s idt_load.s gdt_flush.s pit_handler.s irq_e.s isr_e.s
+SOURCES_ASM = boot.s idt_load.s gdt_flush.s pit_handler.s irq_e.s isr_e.s tss.s
 OBJECTS = $(SOURCES_ASM:.s=.o) $(SOURCES_C:.c=.o)
 
 ISO_DIR = isodir
diff --git a/gdt.c b/gdt.c
index 1d4ca72..eddd3ae 100644
--- a/gdt.c
+++ b/gdt.c
@@ -1,29 +1,69 @@
 #include "gdt.h"
+#include "string.h"
 
-struct gdt_entry gdt[3];
-struct gdt_ptr gdtp;
+#define GDT_ENTRY 6
+
+Gdt_entry gdt[GDT_ENTRY];
+Gdt_ptr gdtp;
 
 extern void gdt_flush(uint32_t);
 
-void gdt_set_gate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
-    gdt[num].base_low = (base & 0xFFFF);
+Tss_entry tss;
+extern void tss_flush(void);
+
+static void gdt_set_gate(uint8_t num, uint32_t base, uint32_t limit, uint8_t access, uint8_t granularity)
+{
+    gdt[num].base_low = base & 0xFFFF;
     gdt[num].base_middle = (base >> 16) & 0xFF;
     gdt[num].base_high = (base >> 24) & 0xFF;
 
-    gdt[num].limit_low = (limit & 0xFFFF);
-    gdt[num].granularity = (limit >> 16) & 0x0F;
+    gdt[num].limit_low = limit & 0xFFFF;
+
+    gdt[num].granularity = (limit >> 16) & 0xF;
+    gdt[num].granularity |= (granularity & 0xF0);
 
-    gdt[num].granularity |= gran & 0xF0;
     gdt[num].access = access;
 }
 
-void gdt_install() {
-    gdtp.limit = (sizeof(struct gdt_entry) * 3) - 1;
+static void tss_install(uint8_t num, uint16_t kernel_ss, uint16_t kernel_esp)
+{
+    uint32_t base = (uint32_t)&tss;
+    uint32_t limit = base + sizeof(Tss_entry);
+
+    gdt_set_gate(num, base, limit, 0xE9, 0x0);
+
+    memset(&tss, 0, sizeof(Tss_entry));
+
+    tss.ss0 = kernel_ss;
+    tss.esp0 = kernel_esp;
+
+    tss.cs = 0x0B;
+    tss.ss = 0x13;
+    tss.es = 0x13;
+    tss.ds = 0x13;
+    tss.fs = 0x13;
+    tss.gs = 0x13;
+}
+
+void set_kernel_stack(uint32_t stack)
+{
+    tss.esp0 = stack;
+}
+
+void gdt_install()
+{
+
+    gdt_set_gate(0, 0x0, 0x0, 0x0, 0x0);          // Null segment
+    gdt_set_gate(1, 0x0, 0xFFFFFFFF, 0x9A, 0xCF); // Kernel code segment
+    gdt_set_gate(2, 0x0, 0xFFFFFFFF, 0x92, 0xCF); // Data segment
+    gdt_set_gate(3, 0x0, 0xFFFFFFFF, 0xFA, 0xCF); // User code segment
+    gdt_set_gate(4, 0x0, 0xFFFFFFFF, 0xF2, 0xCF); // User data segment
+
+    tss_install(5, 0x10, 0x0);
+
+    gdtp.limit = (sizeof(Gdt_entry) * GDT_ENTRY) - 1;
     gdtp.base = (uint32_t)&gdt;
 
-    gdt_set_gate(0, 0, 0, 0, 0);                // Null segment
-    gdt_set_gate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF); // Code segment
-    gdt_set_gate(2, 0, 0xFFFFFFFF, 0x92, 0xCF); // Data segment
-
     gdt_flush((uint32_t)&gdtp);
+    tss_flush();
 }
diff --git a/gdt.h b/gdt.h
index 25c63ca..89946f1 100644
--- a/gdt.h
+++ b/gdt.h
@@ -3,7 +3,9 @@
 
 #include <stdint.h>
 
-struct gdt_entry {
+typedef struct gdt_entry_t Gdt_entry;
+struct gdt_entry_t
+{
     uint16_t limit_low;
     uint16_t base_low;
     uint8_t base_middle;
@@ -12,15 +14,48 @@ struct gdt_entry {
     uint8_t base_high;
 } __attribute__((packed));
 
-struct gdt_ptr {
+typedef struct gdt_ptr_t Gdt_ptr;
+struct gdt_ptr_t
+{
     uint16_t limit;
     uint32_t base;
 } __attribute__((packed));
 
-extern struct gdt_entry gdt[3];
-extern struct gdt_ptr gdtp;
-
-void gdt_set_gate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran);
+static void gdt_set_gate(uint8_t num, uint32_t base, uint32_t limit, uint8_t access, uint8_t granularity);
 void gdt_install();
 
+void set_kernel_stack(uint32_t stack);
+
+typedef struct tss_entry_t Tss_entry;
+struct tss_entry_t
+{
+    uint32_t prevTss;
+    uint32_t esp0;
+    uint32_t ss0;
+    uint32_t esp1;
+    uint32_t ss1;
+    uint32_t esp2;
+    uint32_t ss2;
+    uint32_t cr3;
+    uint32_t eip;
+    uint32_t eflags;
+    uint32_t eax;
+    uint32_t ecx;
+    uint32_t edx;
+    uint32_t ebx;
+    uint32_t esp;
+    uint32_t ebp;
+    uint32_t esi;
+    uint32_t edi;
+    uint32_t es;
+    uint32_t cs;
+    uint32_t ss;
+    uint32_t ds;
+    uint32_t fs;
+    uint32_t gs;
+    uint32_t ldt;
+    uint16_t trap;
+    uint16_t iomap;
+} __attribute__((packed));
+
 #endif
\ No newline at end of file
diff --git a/grub.cfg b/grub.cfg
index 2038825..1ec4b55 100644
--- a/grub.cfg
+++ b/grub.cfg
@@ -1,3 +1,6 @@
+default=0
+timeout=0
+
 menuentry "deadOS" {
 	multiboot /boot/deados.bin
 }
\ No newline at end of file
diff --git a/idt.c b/idt.c
index fbb6bcd..89f3559 100644
--- a/idt.c
+++ b/idt.c
@@ -1,10 +1,12 @@
 #include "idt.h"
 #include "io.h"
+#include "string.h"
 #include <stdint.h>
 
 #define IDT_ENTRIES 256
 
-struct idt_entry {
+struct idt_entry
+{
     uint16_t base_lo;
     uint16_t sel;
     uint8_t always0;
@@ -12,7 +14,8 @@ struct idt_entry {
     uint16_t base_hi;
 } __attribute__((packed));
 
-struct idt_ptr {
+struct idt_ptr
+{
     uint16_t limit;
     uint32_t base;
 } __attribute__((packed));
@@ -20,7 +23,8 @@ struct idt_ptr {
 struct idt_entry idt[IDT_ENTRIES];
 struct idt_ptr idtp;
 
-void idt_set_gate(uint8_t num, uint32_t base, uint16_t sel, uint8_t flags) {
+void idt_set_gate(uint8_t num, uint32_t base, uint16_t sel, uint8_t flags)
+{
     idt[num].base_lo = base & 0xFFFF;
     idt[num].base_hi = (base >> 16) & 0xFFFF;
     idt[num].sel = sel;
@@ -28,28 +32,12 @@ void idt_set_gate(uint8_t num, uint32_t base, uint16_t sel, uint8_t flags) {
     idt[num].flags = flags | 0x60;
 }
 
-void idt_install() {
+void idt_install()
+{
     idtp.limit = (sizeof(struct idt_entry) * IDT_ENTRIES) - 1;
     idtp.base = (uint32_t)&idt;
+
+    memset(&idt, 0, sizeof(struct idt_entry) * IDT_ENTRIES);
+
     idt_load();
 }
-
-void pic_remap(int offset1, int offset2) {
-    unsigned char a1, a2;
-
-    a1 = inb(0x21);
-    a2 = inb(0xA1);
-
-    outb(0x20, 0x11);
-    outb(0xA0, 0x11);
-    outb(0x21, offset1);
-    outb(0xA1, offset2);
-    outb(0x21, 0x04);
-    outb(0xA1, 0x02);
-
-    outb(0x21, 0x01);
-    outb(0xA1, 0x01);
-
-    outb(0x21, a1);
-    outb(0xA1, a2);
-}
\ No newline at end of file
diff --git a/kernel.c b/kernel.c
index db4538a..d6cccf8 100644
--- a/kernel.c
+++ b/kernel.c
@@ -18,7 +18,6 @@ void kernel_main(void)
     gdt_install();
 
     idt_install();
-
     isr_install();
     irq_install();
 
@@ -26,20 +25,18 @@ void kernel_main(void)
 
     keyboard_install();
 
-    sys_enable_interrupts();
-
-    terminal_printc("Hello, &ekernel &7World!\n&5Magenta String Example\nThis is a &4red string&7.\n");
+    terminal_printc("Welcome to &cDeadOS&7.\n");
     for (int i = 0; i < 3; i++)
     {
         terminal_printc("&cDead &7");
         terminal_putchar('0' + (i / 10));
         terminal_putchar('0' + (i % 10));
         terminal_printc("\n");
-        delay(500);
+        delay(100);
     }
-    // syscall_init();
+    syscall_init();
 
-    // enter_user_space();
+    enter_user_space();
 
     shell_init();
 }
\ No newline at end of file
diff --git a/shell.c b/shell.c
index a1869e8..ce8802d 100644
--- a/shell.c
+++ b/shell.c
@@ -80,7 +80,7 @@ void shell_echo_command(char *input)
 void shell_parse_input(char *input)
 {
     char *command = strtok(input, " \n");
-    char *first_param = strtok(NULL, " \n");
+    char *args = input + strlen(command) + 1;
 
     if (command == NULL || *command == '\0')
     {
@@ -93,7 +93,7 @@ void shell_parse_input(char *input)
     }
     else if (strcmp(command, "echo") == 0)
     {
-        shell_echo_command(first_param);
+        shell_echo_command(args);
     }
     else if (strcmp(command, "exit") == 0)
     {
diff --git a/string.c b/string.c
index 36119de..9b9436c 100644
--- a/string.c
+++ b/string.c
@@ -1,6 +1,26 @@
 #include "string.h"
 #include <stddef.h>
 
+size_t strlen(const char *str)
+{
+    size_t len = 0;
+
+    while (str[len])
+        ++len;
+
+    return len;
+}
+
+void *memset(void *ptr, int value, size_t size)
+{
+    unsigned char *buf = (unsigned char *)ptr;
+
+    for (size_t i = 0; i < size; ++i)
+        buf[i] = (unsigned char)value;
+
+    return ptr;
+}
+
 int strcmp(const char *str1, const char *str2)
 {
     while (*str1 && (*str1 == *str2))
@@ -11,17 +31,17 @@ int strcmp(const char *str1, const char *str2)
     return *(const unsigned char *)str1 - *(const unsigned char *)str2;
 }
 
-char *strchr(const char *str, int c)
+char *strchr(const char *str, int character)
 {
-    while (*str != '\0')
+    size_t i = 0;
+    while (str[i] != (char)character)
     {
-        if (*str == c)
-        {
-            return (char *)str;
-        }
-        str++;
+        if (str[i] == '\0')
+            return NULL;
+        ++i;
     }
-    return NULL;
+
+    return (char *)(str + i);
 }
 
 char *strtok(char *str, const char *delim)
diff --git a/string.h b/string.h
index db9d985..048416a 100644
--- a/string.h
+++ b/string.h
@@ -1,8 +1,13 @@
 #ifndef STRING_H
 #define STRING_H
 
+#include <stddef.h>
+
 char *strchr(const char *str, int c);
 char *strtok(char *str, const char *delim);
 int strcmp(const char *str1, const char *str2);
+size_t strlen(const char *str);
+
+void *memset(void *ptr, int value, size_t size);
 
 #endif
\ No newline at end of file
diff --git a/syscall.c b/syscall.c
index 26eac7b..cad9597 100644
--- a/syscall.c
+++ b/syscall.c
@@ -1,23 +1,51 @@
 #include <stdint.h>
+
 #include "interrupts.h"
+#include "keyboard.h"
+#include "sys.h"
 #include "syscall.h"
 #include "tty.h"
 
-void test_syscall()
-{
-    terminal_printc("Test syscall called\n");
-}
+#define NB_SYSCALL 8
+
+void *syscalls[NB_SYSCALL] = {
+    terminal_writestring,
+    keyboard_getchar,
+    terminal_printc,
+    terminal_clear,
+    terminal_putchar,
+    terminal_putentryat,
+    keyboard_clear_buffer,
+
+    sys_halt};
 
 void syscall_handler(Stack *registers)
 {
+    terminal_writestring("Syscall\n");
+
     int sys_index = registers->eax;
 
-    if (sys_index != 0)
-    {
+    if (sys_index >= NB_SYSCALL)
         return;
-    }
 
-    test_syscall();
+    void *function = syscalls[sys_index];
+
+    int ret;
+    asm volatile("   push %1;   \
+                     push %2;   \
+                     push %3;   \
+                     push %4;   \
+                     push %5;   \
+                     call *%6;  \
+                     pop %%ebx; \
+                     pop %%ebx; \
+                     pop %%ebx; \
+                     pop %%ebx; \
+                     pop %%ebx; \
+                     " : "=a"(ret) : "r"(registers->edi), "r"(registers->esi),
+                                     "r"(registers->edx), "r"(registers->ecx),
+                                     "r"(registers->ebx), "r"(function));
+    registers->eax = ret;
 }
 
 void syscall_init(void)
diff --git a/timer.c b/timer.c
index 6a6d1e6..1159cb3 100644
--- a/timer.c
+++ b/timer.c
@@ -15,6 +15,27 @@ void pit_handler()
     outb(0x20, 0x20);
 }
 
+void pic_remap(int offset1, int offset2)
+{
+    unsigned char a1, a2;
+
+    a1 = inb(0x21);
+    a2 = inb(0xA1);
+
+    outb(0x20, 0x11);
+    outb(0xA0, 0x11);
+    outb(0x21, offset1);
+    outb(0xA1, offset2);
+    outb(0x21, 0x04);
+    outb(0xA1, 0x02);
+
+    outb(0x21, 0x01);
+    outb(0xA1, 0x01);
+
+    outb(0x21, a1);
+    outb(0xA1, a2);
+}
+
 void delay(uint32_t milliseconds)
 {
     uint32_t end = tick + milliseconds;
diff --git a/tss.s b/tss.s
new file mode 100644
index 0000000..8e3c53f
--- /dev/null
+++ b/tss.s
@@ -0,0 +1,9 @@
+.section .text
+.align 4
+
+.global tss_flush
+.type tss_flush, @function
+tss_flush:
+    mov $0x2B, %ax
+    ltr %ax
+    ret
\ No newline at end of file
diff --git a/tty.c b/tty.c
index 72fb0e9..06420ae 100644
--- a/tty.c
+++ b/tty.c
@@ -4,14 +4,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
-
-size_t strlen(const char *str)
-{
-    size_t len = 0;
-    while (str[len])
-        len++;
-    return len;
-}
+#include "string.h"
 
 static const size_t VGA_WIDTH = 80;
 static const size_t VGA_HEIGHT = 25;
diff --git a/user_space.c b/user_space.c
index fdc633a..34559bc 100644
--- a/user_space.c
+++ b/user_space.c
@@ -1,8 +1,10 @@
 #include "user_space.h"
+#include "gdt.h"
 
 void enter_user_space(void)
 {
-    asm volatile(" cli;              \
+    set_kernel_stack(0x110); // 128KB ?? WHY? ??
+    asm volatile("cli;              \
                   mov $0x23, %ax;   \
                   mov %ax, %ds;     \
                   mov %ax, %es;     \