Data segments
Str1 db
Str2 db
Data end 

Code segment 
Assumes:code, ds:Data
Start:
Mov ax, Data
Mov ds, ax
Mov dx, offset Str1
Mov ah, 09h
Int 21h
Call delay 100ms
Mov dx, offset Str2
Int ah, 09h
Int 21h
Mov ah, 4ch
Int 21h
Delay proc near 
Mov ex, 0fffh
n1:loop n1
Ret
Delay endp
Stack segment 
Stack ends
Data segment
Val DB 'A'
Data ends

Start:
     Space macro
     Mov DL, 
     Mov ah, 02;
     Int 21h
     Endm
     
     Mov AX, @Data
     Mov DS, AX
     mov CL, 26
     MOV DL, 65
     
     PRINT:
     MOV AH, 02H
     Int 21h
     Push dx
     Space
     Pop dx
     Inc DL
     Dec CL
     Jnz PRINT
     Mov ah, 4ch
     Int 21h
     
     Main Endm
     End start