CODE SEGMENT

; Set DS register

MOV AX, DATA     ;    boiler plate code to set the DS register so that the

MOV DS, AX          ;    program can access the data segment.

; read first digit from keyboard

                MOV AH, 08

INT   21H

MOV BL, AL

SUB BL, '0'

MUL BL, 10H

; read second digit from keyboard

MOV   AH, 08H

INT    21H

MOV   DL, AL

SUB   DL, '0'

; DL = 9 AND BL = 30 

SUM     BL, DL

; Now BL store 39

CODE ENDS.

Note: Boilerplate code is the code which is present less or more in the similar form in each assembly language program.