Question

汇编高手请进来帮下忙

下面是一个十六进制到二进制转换的程序中的一部分。

LEA DX,DISPLAY
MOV AH,9H
INT 21H

CALL GETNUM
MOV CX,0010H
MOV BX,DX
TTT: ROL BX,1
MOV DL,BL
AND DL,01H
ADD DL,30H
MOV AH,02H
INT 21H
LOOP TTT
MOV AX,4C00H
INT 21H
ret
main endp
GETNUM PROC NEAR
PUSH CX
XOR DX,DX
GGG: MOV AH,01H
INT 21H
CMP AL,0DH
JZ PPP
CMP AL,30H
JZ KKK
SUB AL,30H
CMP AL, 0AH
JB GETS
CMP AL,11H
JB KKK
SUB AL,07H
CMP AL,0FH
JBE GETS
CMP AL,2AH
JB KKK
CMP AL,2FH
JA KKK
CMP AL,2FH
SUB AL,20H
GETS: MOV CL,04
SHL DX,CL
XOR AH,AH
ADD DX,AX
JMP GGG
KKK: LEA DX,ERROR
MOV AH,02H
INT 21H
PPP: LEA DX,ENTER
MOV AH,02H
INT 21H
RET
GETNUM ENDP
program ends
end start

我想问一下下面这些每个都是干吗的阿？麻烦给详细的讲下。

ADD DL,30H
CMP AL,0DH
CMP AL,30H
SUB AL,30H
CMP AL,0AH
CMP AL,11H
SUB AL,07H
CMP AL,0FH
CMP AL,2AH
CMP AL,2FH
CMP AL,2FH
SUB AL,20H

Answer 1

LEA DX,DISPLAY
MOV AH,9H
INT 21H

CALL GETNUM
MOV CX,0010H
MOV BX,DX
TTT: ROL BX,1
MOV DL,BL
AND DL,01H
ADD DL,30H
MOV AH,02H
INT 21H
LOOP TTT
MOV AX,4C00H
INT 21H
ret
main endp
GETNUM PROC NEAR
PUSH CX
XOR DX,DX
GGG: MOV AH,01H
INT 21H
CMP AL,0DH
JZ PPP
CMP AL,30H
JZ KKK
SUB AL,30H
CMP AL, 0AH
JB GETS
CMP AL,11H
JB KKK
SUB AL,07H
CMP AL,0FH
JBE GETS
CMP AL,2AH
JB KKK
CMP AL,2FH
JA KKK
CMP AL,2FH
SUB AL,20H
GETS: MOV CL,04
SHL DX,CL
XOR AH,AH
ADD DX,AX
JMP GGG
KKK: LEA DX,ERROR
MOV AH,02H
INT 21H
PPP: LEA DX,ENTER
MOV AH,02H
INT 21H
RET
GETNUM ENDP
program ends
end start

我想问一下下面这些每个都是干吗的阿？麻烦给详细的讲下。

ADD DL,30H
CMP AL,0DH
CMP AL,30H
SUB AL,30H
CMP AL,0AH
CMP AL,11H
SUB AL,07H
CMP AL,0FH
CMP AL,2AH
CMP AL,2FH
CMP AL,2FH
SUB AL,20H