Cann't print char on the screen ?

I wrote a small program . But it didn't work well. The bios interrupt seemed working but no char was printed
on the screen . The cursor moved but there was no char on the black screen.I have not found the reason , please .
Here is the code (short but all):

      BOOTSEG     equ   0x07c0
      SYSSEG      equ   0x1000
      SYSLEN      equ   17
beg:
      jmp   BOOTSEG:go
go:
      mov   ax , cs
      mov   ds , ax
      mov   es , ax
      mov   ss , ax
      mov   sp , 0x400

load_system:
      mov   ax , SYSSEG
      mov   es , ax        
      mov   ax , 0x0200+SYSLEN
      mov   cx , 0x0002  
      mov   dx , 0x0000  
      mov   bx , 0x0000
      int   0x13
      jnc   ok_load
      mov   ah , 0
      int   0x13
      jmp   load_system    

ok_load:
      cli
      mov   ax , BOOTSEG
      mov   ds , ax
      jmp   SYSSEG:0
      times 510-($-$$) db 0
      dw    0xaa55

      mov   ax , cs
      mov   ds , ax
      mov   es , ax
      mov   ax , begtrack
      mov   ss , ax
      mov   sp , track
      sti
      mov   ax , 0x1301
      mov   bx , 0x0004
      mov   cx , 15
      mov   dx , 0x0000
      mov   bp , showSomething
      int   0x10
      jmp   $+2
re:   jmp   re

begtrack:
      times 128   db    0
track:
      times 200   dd    0

showSomething:
      db    'In the kernel'
      db    0x0d,0x0a