diff --git a/kernel/boot/bootx64.asm b/kernel/boot/bootx64.asm
index e1bb666..b482a80 100644
--- a/kernel/boot/bootx64.asm
+++ b/kernel/boot/bootx64.asm
@@ -45,7 +45,7 @@ proc main _efi_handle, _efi_table
         mov     rcx, [rbx+EFI_SYSTEM_TABLE.ConOut]
         fstcall [rcx+EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.Reset], rcx, 1
         test    eax, eax
-        jnz     $       ; what can I do here?
+        jnz     $ ; loop if fail to init text
 
         fstcall set_text_color, EFI_BLUE or EFI_BACKGROUND_GREEN
         fstcall print_string, msg_hello_k64_loader
@@ -53,7 +53,7 @@ proc main _efi_handle, _efi_table
         fstcall set_text_color, EFI_LIGHTRED
         fstcall print_string, msg_2
 
-        ;; TODO: print some dec, hex. => impl simple printf
+        ;; TODO: print some dec, hex. => impl simple printf. fdo.inc
 
         jmp     $
 endp
diff --git a/kernel/fdo.inc b/kernel/fdo.inc
new file mode 100644
index 0000000..2e7d4a2
--- /dev/null
+++ b/kernel/fdo.inc
@@ -0,0 +1 @@
+; TODO printf impl here
\ No newline at end of file
diff --git a/kernel/printf.inc b/kernel/printf.inc
deleted file mode 100644
index e69de29..0000000