嗨，我遇到了这段代码的问题。根据我教授提供给我们的符号列表，它将打印0-9精细但A-F或a-f它只是给我一个笑脸甚至不是至少ASCII符号。这是我的代码。请帮忙。我正在使用NASM和DosBox。
org 100h
; hexadecimal to base 10 conversion program
section .data
MSG1 dw " Enter a hexadecimal digit ", '$'
MSG2 dw " In decimal it is: ", '$'
MSG3 dw " Do you want to do it again? ", '$'
EMSG dw " Illegal character, enter 0..9 or A..F: ", '$'
section .text
main:
; print user prompt
mov dx, MSG1 ; get message
mov ah, 09h ; display string function
int 21h ; display it
jmp userin ; jumps to user input so if illegal character is entered message won't display again
userin:
; input a hexidecimal number then compare to ASCII codes
mov ah, 01h ; keyboard input function
int 21h ; character input, copies character into al
mov bh, al ; moves al into bh to avoid al being messed with
cmp bh, 30h ; compares input to ASCII code for 0
jl error ; if input is less than 0 jump to main
cmp bh, 39h ; compares input to ASCII code for 9
jle print1 ; if input is less than or equal to 9 jump to print
cmp bh, 41h ; compares input to ASCII code for 'A'
jl error ; if input is less than 'A' jump to main
cmp bh, 46h ; compares input to ASCII code for 'F'
jle convert1 ; if input is less than or equal to 'F' jump to convert1
cmp bh, 61h ; compares input to ASCII code for 'a'
jl error ; if input is less than 'a' jump to main
cmp bh, 66h ; compares input to ASCII code for 'f'
jle convert2 ; if input is less than of equal to 'f' jump to convert2
jg error ; if input is greater than 'z' jump to main
error:
; displays error message then jumps back
mov dx, EMSG ; moves error message into display string register
mov ah, 09h ; display string function
int 21h ; displays it
jmp userin ; jumps back to user input
convert1:
; converts input from hexadecimal A-F to decimal
sub bh, 16 ; subtracts 0Fh from input to get decimal
jmp print2 ; jumps to print
convert2:
; converts input from hexidecimal a-f to decimal
sub bh, 48 ; subtracts 30h from the input to get
jmp print2 ; jumps to print
print1:
; prints the input in decimal form
mov dx, MSG2 ; moves MSG2 into display string register
mov ah, 09h ; display string function
int 21h ; display MSG2 "In decimal it is:"
mov dl, bh ; moves input into display character register
mov ah, 02h ; display character function
int 21h ; display input in decimal form
jmp again ; jumps to again
print2:
;prints the input in decimal form
mov dx, MSG2 ; moves MSG2 into display string register
mov ah, 09h ; display string function
int 21h ; display MSG2 "In decimal it is:"
mov dl, 1d ; will add 10 to the converted ASCII code
mov ah, 02h ; display character function
int 21h ; display 1 in front of input in decimal form
mov dl, bh ; moves converted input to display character register
mov ah, 02h ; display character function
int 21h ; displays converted input
jmp again ; jumps to again
again:
; asks if user wants to do it again
mov dx, MSG3 ; moves MSG2 into display string register
mov ah, 09h ; display string function
int 21h ; display MSG3 "Do you want to do it again?"
mov ah, 01h ; keyboard input function
int 21h ; character input, copies into al
cmp al, 59h ; compares input to ASCII code for 'Y'
je main ; if input is equal to 'Y' jump to main
jl exit ; if input is less than 'Y' jump to exit
cmp al, 79h ; compares input to ASCII code for 'y'
je main ; if input is equal to 'y' jump to main
jne exit ; if input is not equal to 'y' jump to exit
exit:
;exit to DOS
mov ah, 04Ch ; DOS function: Exit program
mov al, 0 ; Return exit code value
int 21h ; Call DOS. Terminate program
答案 0 :(得分：2)
计算是正确的，但应该打印前导'1'的代码是错误的。您需要将字符代码放在DL中，而不是数字。而不是
mov dl, 1d ; will add 10 to the converted ASCII code
mov ah, 02h ; display character function
int 21h ; display 1 in front of input in decimal form
应该是
mov dl, 49 ; will add 10 to the converted ASCII code
mov ah, 02h ; display character function
int 21h ; display 1 in front of input in decimal form