format MZ
entry code_seg:start; set entry point
stack 256
segment data_seg
; add your data here!
message db "Input two hexadecimal digits,$"
tabl db 48 dup (0),0,1,2,3,4,5,6,7,8,9,7 dup (0)
     db 0ah,0bh,0ch,0dh,0eh,0fh,26 dup (0)
     db 0ah,0bh,0ch,0dh,0eh,0fh,152 dup (0)
segment code_seg
start:
; set segment registers:
mov ax,data_seg
mov ds,ax
mov es,ax
; add your code here
lea bx,[tabl]
mov ah,9
mov dx,message
int 21h
xor ax,ax
mov ah,1h
int 21h
xlat
mov dl,al
shl dl,4
int 21h
xlat
add al,dl
mov ax,4c00h
int 21h    

aram@linux-39o6:~/Documents> fasm PRG_7_3-DOS.asm
flat assembler  version 1.67.33  (16384 kilobytes memory)
PRG_7_3-DOS.asm [24]:
xlat
error: invalid operand.    

xlat replaces a byte in the AL register with a byte indexed by its value in a translation table addressed by BX or EBX. The operand should be a byte memory addressed by BX or EBX with any segment prefix. This instruction has also a short form xlatb which has no operands and uses the BX or EBX address in the segment selected by DS depending on the current code setting