请教，为什么输出的不是0100100b 啊？

[Start13]

DATA segment
TAB db 1000000b,1111001b,0100100b,0110000b
input db 2
output db ?
data ends

   cseg segment
           assume cs:cseg,ds:data
   start:  mov ax,data
           mov ds,ax

           mov bl,input
           and bl,0Fh
           xor bh,bh
           mov al,tab[bx]
           mov output,al     
           mov dl,output
           xor dh,dh
                   
           add dx,30h
           mov ah,02h
           int 21h
           mov ah,4ch
           int 21H
   cseg    ends
           end start

[killbug2004]

DATA segment
TAB db 1000000b,1111001b,0100100b,0110000b;tab db 0x40,0x79,0x24,0x30
input db 2
output db ?
data ends

   cseg segment
           assume cs:cseg,ds:data
   start:  mov ax,data
           mov ds,ax

           mov bl,input
           and bl,0Fh
           xor bh,bh	;bh = 0
           		;bx = 2
           
           mov al,tab[bx];al = 0100100b = 0x24
           mov output,al     
           mov dl,output
           xor dh,dh	;dh = 0
           		;dx = 0x24
                   
           add dx,30h	;dx = 0x54 = 'T'
           mov ah,02h
           int 21h
           
           mov ah,4ch
           int 21H
   cseg    ends
           end start

中断INT 21H :
(2)、功能02H
功能描述：向标准输出设备(如：屏幕)输出一个字符。该输出还可被重定向，如果这样做，则将无法判断磁盘是否满
入口参数：AH＝02H
DL＝待输出字符的ASCII码
出口参数：无