.MODEL SMALL .STACK 100H .DATA PROMPT DB \'Enter the character : $\' MSG_1 DB \'The input letter is : $\' MSG_2 DB \'The input character is not an Upper Case Letter.$\' .CODE MAIN PROC MOV AX, @DATA ; initialize DS MOV DS, AX LEA DX, PROMPT ; load and print PROMPT MOV AH, 9 INT 21H MOV AH, 1 ; read a character INT 21H MOV BL, AL ; save the input character into BL MOV AH, 2 ; carriage return MOV DL, 0DH INT 21H MOV DL, 0AH ; line feed INT 21H CMP BL, \"A\" ; compare input character and \"A\" JB @DISPLAY ; jump to label @DISPLAY if input<A CMP BL, \"Z\" ; compare input character and \"Z\" JA @DISPLAY ; jump to label @DISPLAY if input>Z LEA DX,MSG_1 ; load and print MSG_1 MOV AH, 9 INT 21H MOV AH, 2 ; print the character MOV DL, BL INT 21H JMP @EXIT ; jump to label @EXIT @DISPLAY: ; jump label LEA DX,MSG_2 ; load and print MSG_2 MOV AH, 9 INT 21H @EXIT: ; jump label MOV AH, 4CH ; return control to DOS INT 21H MAIN ENDP END MAIN