DATA SEGMENT

    S DB 'HELLO','$'

DATA ENDS

CODE SEGMENT

ASSUME CS:CODE, DS:DATA

START:

    MOV AX, DATA       ; Load data segment address

    MOV DS, AX         ; Move it to DS

    LEA SI, S          ; Load address of string S into SI

    MOV AH, 09H        ; Function 09h: display string till '$'

    INT 21H

    ; Find length of the string

    LEA SI, S

    MOV CX, 0

FIND_LEN:

    MOV AL, [SI]

    CMP AL, '$'

    JZ REV

    INC SI

    INC CX

    JMP FIND_LEN

REV:

    DEC SI             ; SI now points to last character before '$'

REVERSE_STRING:

    MOV AH, 02H        ; Function 02h: display character in DL

    MOV DL, [SI]

    INT 21H

    DEC SI

    LOOP REVERSE_STRING

    MOV AH, 4CH        ; Exit program

    INT 21H

CODE ENDS

END START