org 100h

jmp main
    chrs db  'M','I','M','I','H','S','G','A','M','$'

main:
    mov bp, sp

    mov ax,offset chrs
    call print_ax_str
    mov ax, offset chrs
    push ax
    push 9
    call reverse
    PRINTN
    mov ax,offset chrs
    call print_ax_str

    jmp stop

reverse proc
    i equ -2
    temp equ -4

    ; First save the old BP
    push bp
    push bx
    push si
    push ax
    ; Now establish new BP
    mov bp, sp
    ;make space for 2 local variables
    sub sp, 4

    ;write your code here:
    mov si, [bp+12]

    mov bx, [bp+10]
    mov [bp+i], bx
    dec [bp+i]      ; [bp+i]=len-1

    for:
        ; temp=str[i]
        mov bx, [bp+i]
        mov bx, [si+bx]
        mov [bp+temp], bl

        ; str[i]=str[len-1-i]
        mov ax, [bp+i]      ; ax=i
        mov bx, [bp+10]     ; bx=len
        sub bx, ax          ; bx=len-i
        mov bl, [si+bx-1]   ; bx=str[len-i-1]
        xchg ax, bx         ; al=str[len-i-1]
        mov bx, si          ; bx=str
        add bx, [bp+i]      ; bx=str+i
        mov [bx], al        ; str[i]=str[len-i-1]

        ; str[len-1-i]=temp
        mov ax, [bp+i]      ; ax=i
        mov bx, [bp+10]     ; bx=len
        sub bx, ax          ; bx=len-i
        mov al, [bp+temp]   ; al=temp
        mov [si+bx-1], al   ; str[len-i-1]=temp

        ; i--
        dec [bp+i]

        ; i>=len/2
        mov ax, [bp+10]     ; ax=len
        shr ax, 1           ; ax=len/2

        cmp [bp+i], ax      ; i-len/2
        jae for




    mov sp, bp
    ; Restore OLD BP
    pop ax
    pop si
    pop bx
    pop bp
    ret 4
reverse endp

stop:
    mov ah, 0
    int 16h
    ret

include magshimim.inc