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@ -5,20 +5,23 @@ print_hex:
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mov cx, 0 ; our index variable
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; Strategy: get the last char of 'dx', then convert to ASCII
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; ASCII values: '0' (ASCII 0x30) to '9' (0x39), so just add 0x30 to byte N.
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; Then, move the ASCII byte to the correct position on the resulting string
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loop:
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cmp cx, 4 ; loop 4 times
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je end
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mov ax, dx ; we will work on ax
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; 1. convert last char of 'dx' to ascii
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mov ax, dx ; we will use 'ax' as our working register
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and ax, 0x000f ; 0x1234 -> 0x0004 by masking first three to zeros
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; convert each hex value to its ASCII value. '0' (ASCII 0x30) to '9' (0x39)
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; We will need to convert byte N to byte 0x3N by just adding 0x30
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add ax, 0x30 ; 0x0004 -> ASCII '4'
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; bx <- address of the character to replace = base + string length - index
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mov bx, HEX_OUT + 5 ; last char of string, beware not to replace null char
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sub bx, cx ; address of char to replace
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or [bx], ax ; copy the ASCII char to the string position
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add ax, 0x30 ; add 0x30 to N to convert it to ASCII "N"
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; 2. get the correct position of the string to place our ASCII char
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; bx <- base address + string length - index of char
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mov bx, HEX_OUT + 5 ; base + length
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sub bx, cx ; our index variable
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or [bx], ax ; copy the ASCII char on 'ax' to the position pointed by 'bx'
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ror dx, 4 ; 0x1234 -> 0x4123 -> 0x3412 -> 0x2341 -> 0x1234
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; increment index and loop
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