org  100h


print_new_line macro
    mov dl, 13
    mov ah, 2
    int 21h   
    mov dl, 10
    mov ah, 2
    int 21h      
endm


    mov dx, offset msg1
    mov ah, 9
    int 21h
    ; input the string:
    mov dx, offset s1
    mov ah, 0ah
    int 21h
    
    ; get actual string size:
    xor cx, cx
    mov cl, s1[1]
    print_new_line
                  
    mov bx, offset s1[2]
print_char:
    mov dl, [bx]
    mov ah, 2
    int 21h      
    print_new_line   
    inc bx
    loop print_char


    ; wait for any key...
    mov ax, 0 
    int 16h
    
    ret


msg1    db  "ENTER THE STRING: $"
s1      db 100,?, 100 dup(' ') 


end
     

; Input:
;
; DS:SI = offset to input buffer
; (first byte specifies size)
;
Input:
    mov ah, 01h         ; Select DOS "Input with echo" function
    mov cl, [ di ]      ; Grab size of buffer into CL (max size)
    mov ch, cl          ; Copy into CH (current count)
    inc di              ; Advance to start of actual buffer
NextChar:
    int 21h             ; Input character from "stdin"
    cmp al, 0Dh         ; Is it ENTER?
    je EndOfInput       ; Yes, then terminate early
    cmp al, 08h         ; Is it backspace?
    jne CarryOn         ; No, then skip over backspace processing

    cmp ch, cl          ; Are we at the start of the buffer?
    je NextChar         ; Yes, ignore backspace as we can't go back
                        ; before the beginning of the buffer
    dec di              ; Move back a character in the buffer
    inc ch              ; Increment count back up
    mov ah, 02h         ; Select DOS "display output"
    mov dl, 20h         ; A space to clear old character
    int 21h             ; Print it!
    mov dl, 08h         ; A backspace character moves left
                        ; (non-destructive)
    int 21h             ; Print it!
    mov ah, 01h         ; Restore DOS "input with echo" function
    jmp NextChar        ; Jump to get next character

CarryOn:
    mov [ di ], al      ; Store input into buffer
    inc di              ; Advance to next character in buffer
    dec ch              ; Decrement count of characters
    jnz NextChar        ; While there's still room in buffer,
                        ; do it all again
EndOfInput:
    ret    

Thanks a lot for your copy'n paste code But it didn't work. It didn't give any error too. Should i insert sth in it?
I'll tell your wishes to instructor with my wishes, don't worry

lds si,[iBuffer]
call Input
.
.
.
iBuffer db 42,42 dup ?