putc:
  pushf
  push cs
  call isr_putc
  ret

isr_getc:
  xor ax, ax
  int 0x16
  test al, al
  jz isr_getc
isr_putc:
  push bx
  mov ah, 0x0e
  mov bx, 0x0000
  int 0x10
  pop bx
  iret