diff --git a/4_gdt/common.c b/4_gdt/common.c
index b7dfda6..4e691fc 100644
--- a/4_gdt/common.c
+++ b/4_gdt/common.c
@@ -23,67 +23,3 @@ u16int inw(u16int port)
     return ret;
 }
 
-// Copy len bytes from src to dest.
-void memcpy(u8int *dest, const u8int *src, u32int len)
-{
-    const u8int *sp = (const u8int *)src;
-    u8int *dp = (u8int *)dest;
-    for(; len != 0; len--) *dp++ = *sp++;
-}
-
-// Write len copies of val into dest.
-void memset(u8int *dest, u8int val, u32int len)
-{
-    u8int *temp = (u8int *)dest;
-    for ( ; len != 0; len--) *temp++ = val;
-}
-
-// Compare two strings. Should return -1 if 
-// str1 < str2, 0 if they are equal or 1 otherwise.
-int strcmp(char *str1, char *str2)
-{
-      int i = 0;
-      int failed = 0;
-      while(str1[i] != '\0' && str2[i] != '\0')
-      {
-          if(str1[i] != str2[i])
-          {
-              failed = 1;
-              break;
-          }
-          i++;
-      }
-      // why did the loop exit?
-      if( (str1[i] == '\0' && str2[i] != '\0') || (str1[i] != '\0' && str2[i] == '\0') )
-          failed = 1;
-  
-      return failed;
-}
-
-// Copy the NULL-terminated string src into dest, and
-// return dest.
-char *strcpy(char *dest, const char *src)
-{
-    do
-    {
-      *dest++ = *src++;
-    }
-    while (*src != 0);
-}
-
-// Concatenate the NULL-terminated string src onto
-// the end of dest, and return dest.
-char *strcat(char *dest, const char *src)
-{
-    while (*dest != 0)
-    {
-        *dest = *dest++;
-    }
-
-    do
-    {
-        *dest++ = *src++;
-    }
-    while (*src != 0);
-    return dest;
-}
diff --git a/4_gdt/descriptor_tables.c b/4_gdt/descriptor_tables.c
index 16168e6..bf8a8e2 100644
--- a/4_gdt/descriptor_tables.c
+++ b/4_gdt/descriptor_tables.c
@@ -68,7 +68,7 @@ static void init_idt()
     idt_ptr.limit = sizeof(idt_entry_t) * 256 -1;
     idt_ptr.base  = (u32int)&idt_entries;
 
-    memset(&idt_entries, 0, sizeof(idt_entry_t)*256);
+    // memset(&idt_entries, 0, sizeof(idt_entry_t)*256);
 
     idt_set_gate( 0, (u32int)isr0 , 0x08, 0x8E);
     idt_set_gate( 1, (u32int)isr1 , 0x08, 0x8E);