print.s

   1 %define CURRENT_ADDR cs:di
   2
   3 ; Prints a null terminated string of your choice.
   4 ; Arguments:
   5 ;     CS:DI - pointer to the string you want to print
   6 ;     BL - 0 prints newline, otherwise no
   7 print
   8         pusha
   9         mov ah, 0Eh ; teletype print
  10 .write2
  11         mov al, [CURRENT_ADDR] ; get current char and put it in al
  12         cmp al, 0 ; check if al is null (string terminator)
  13         je .newline ; if it is, start a new line
  14         int 10h ; otherwise write the char
  15         inc di ; increment pointer to string
  16         jmp .write2 ; jump back to this section
  17 .newline
  18         cmp bl, 1
  19         je .done
  20         mov al, 0Dh ; carriage return
  21         int 10h
  22         mov al, 0Ah ; line feed
  23         int 10h
  24 .done
  25         popa
  26         ret ; return
  27
  28 ; Prints a word (16-bit value) in hex format.
  29 ; Arguments:
  30 ;     DX - word to print
  31 ;     BL - 0 will print a newline, 1 won't
  32 print_word
  33         pusha ; push all regs to stack
  34         mov di, HEX_OUT+5 ; set destination index to last char in HEX_OUT
  35         mov ax, dx ; copy argument to accumulator
  36         and al, 00001111b ; extract the low nibble of the low half of the accumulator
  37         call .compare ; fill in the string with correct value
  38         dec di ; decrement string pointer
  39         mov ax, dx ; copy argument to accumulator
  40         and al, 11110000b ; extract high nibble of low half of accumulator
  41         shr al, 4 ; shift high nibble to low nibble
  42         call .compare ; fill in string with correct value
  43         dec di
  44         mov al, ah ; copy high portion of accumulator to low
  45         and al, 00001111b ;
  46         call .compare
  47         dec di
  48         mov al, ah
  49         and al, 11110000b
  50         shr al, 4
  51         call .compare
  52         mov di, HEX_OUT
  53         call print ; write string
  54         popa
  55         ret
  56
  57 .compare
  58         cmp al, 0 ; compare al with 0
  59         jne .one ; if not equal, compare with 1
  60         mov byte [CURRENT_ADDR], '0' ; set character to ASCII 0
  61         ret ; return
  62 .one
  63         cmp al, 1
  64         jne .two
  65         mov byte [CURRENT_ADDR], '1'
  66         ret
  67 .two
  68         cmp al, 2
  69         jne .three
  70         mov byte [CURRENT_ADDR], '2'
  71         ret
  72 .three
  73         cmp al, 3
  74         jne .four
  75         mov byte [CURRENT_ADDR], '3'
  76         ret
  77 .four
  78         cmp al, 4
  79         jne .five
  80         mov byte [CURRENT_ADDR], '4'
  81         ret
  82 .five
  83         cmp al, 5
  84         jne .six
  85         mov byte [CURRENT_ADDR], '5'
  86         ret
  87 .six
  88         cmp al, 6
  89         jne .seven
  90         mov byte [CURRENT_ADDR], '6'
  91         ret
  92 .seven
  93         cmp al, 7
  94         jne .eight
  95         mov byte [CURRENT_ADDR], '7'
  96         ret
  97 .eight
  98         cmp al, 8
  99         jne .nine
 100         mov byte [CURRENT_ADDR], '8'
 101         ret
 102 .nine
 103         cmp al, 9
 104         jne .ten
 105         mov byte [CURRENT_ADDR], '9'
 106         ret
 107 .ten
 108         cmp al, 0Ah
 109         jne .eleven
 110         mov byte [CURRENT_ADDR], 'A'
 111         ret
 112 .eleven
 113         cmp al, 0Bh
 114         jne .twelve
 115         mov byte [CURRENT_ADDR], 'B'
 116         ret
 117 .twelve
 118         cmp al, 0Ch
 119         jne .thirteen
 120         mov byte [CURRENT_ADDR], 'C'
 121         ret
 122 .thirteen
 123         cmp al, 0Dh
 124         jne .fourteen
 125         mov byte [CURRENT_ADDR], 'D'
 126         ret
 127 .fourteen
 128         cmp al, 0Eh
 129         jne .fifteen
 130         mov byte [CURRENT_ADDR], 'E'
 131         ret
 132 .fifteen
 133         mov byte [CURRENT_ADDR], 'F'
 134         ret
 135
 136 HEX_OUT db "0x0000", 0