print.s

   1 %define CURRENT_ADDR cs:di
   2
   3 print_word:
   4         pusha ; push all regs to stack
   5         mov di, HEX_OUT+5 ; set destination index to last char in HEX_OUT
   6         mov ax, dx ; copy argument to accumulator
   7         and al, 00001111b ; extract the low nibble of the low half of the accumulator
   8         call .compare ; fill in the string with correct value
   9         dec di ; decrement destination index
  10         mov ax, dx ; copy argument to accumulator
  11         and al, 11110000b ; extract high nibble of low half of accumulator
  12         shr al, 4 ; shift high nibble to low nibble
  13         call .compare ; fill in string with correct value
  14         dec di
  15         mov al, ah ; copy high portion of accumulator to low
  16         and al, 00001111b ;
  17         call .compare
  18         dec di
  19         mov al, ah
  20         and al, 11110000b
  21         shr al, 4
  22         call .compare
  23         jmp .write ; write string
  24
  25 .write:
  26         popa ; get back our arguments
  27         mov dl, cl ; column
  28         mov dh, ch ; row
  29         pusha ; save registers
  30         mov al, 1 ; update cursor
  31         mov bh, 0 ; page number
  32         mov bl, 00000111b ; colors
  33         mov cx, 6 ; length of string
  34         push cs ; push code segment address
  35         pop es ; pop to extra segment address
  36         mov bp, HEX_OUT ; offset to extra segment of string
  37         mov ah, 13h ; write string
  38         int 10h ; BIOS interrupt
  39         popa
  40         ret ; return
  41
  42 .compare:
  43         cmp al, 0 ; compare al with 0
  44         jne .one ; if not equal, compare with 1
  45         mov byte [CURRENT_ADDR], '0' ; set character to ASCII 0
  46         ret ; return
  47 .one:
  48         cmp al, 1
  49         jne .two
  50         mov byte [CURRENT_ADDR], '1'
  51         ret
  52 .two:
  53         cmp al, 2
  54         jne .three
  55         mov byte [CURRENT_ADDR], '2'
  56         ret
  57 .three:
  58         cmp al, 3
  59         jne .four
  60         mov byte [CURRENT_ADDR], '3'
  61         ret
  62 .four:
  63         cmp al, 4
  64         jne .five
  65         mov byte [CURRENT_ADDR], '4'
  66         ret
  67 .five:
  68         cmp al, 5
  69         jne .six
  70         mov byte [CURRENT_ADDR], '5'
  71         ret
  72 .six:
  73         cmp al, 6
  74         jne .seven
  75         mov byte [CURRENT_ADDR], '6'
  76         ret
  77 .seven:
  78         cmp al, 7
  79         jne .eight
  80         mov byte [CURRENT_ADDR], '7'
  81         ret
  82 .eight:
  83         cmp al, 8
  84         jne .nine
  85         mov byte [CURRENT_ADDR], '8'
  86         ret
  87 .nine:
  88         cmp al, 9
  89         jne .ten
  90         mov byte [CURRENT_ADDR], '9'
  91         ret
  92 .ten:
  93         cmp al, 0Ah
  94         jne .eleven
  95         mov byte [CURRENT_ADDR], 'A'
  96         ret
  97 .eleven:
  98         cmp al, 0Bh
  99         jne .twelve
 100         mov byte [CURRENT_ADDR], 'B'
 101         ret
 102 .twelve:
 103         cmp al, 0Ch
 104         jne .thirteen
 105         mov byte [CURRENT_ADDR], 'C'
 106         ret
 107 .thirteen:
 108         cmp al, 0Dh
 109         jne .fourteen
 110         mov byte [CURRENT_ADDR], 'D'
 111         ret
 112 .fourteen:
 113         cmp al, 0Eh
 114         jne .fifteen
 115         mov byte [CURRENT_ADDR], 'E'
 116         ret
 117 .fifteen:
 118         mov byte [CURRENT_ADDR], 'F'
 119         ret
 120
 121 HEX_OUT: db "0x0000"