org 100h
        NL equ 0dh, 0ah

start:

        mov ah, 9 ;output task
        mov dx, taskStr
        int 21h

        mov ah, 0ah ;input - string
        mov dx, buffStr
        int 21h

        mov ah, 2 ;output - new line
        mov dx, 0d0ah
        int 21h

        cld ;direction - forward (df = 0)
        mov si, buffStr ;SOURCE address...
        add si, 12 ;first two bytes MAX_LEN and LEN + tenth symbol = +12
        mov di, destStr ;DESTINATION address
        mov cx, 6 ;10 11 12 13 14 15 - 6 symbols
        rep movsb ;repeat movsb (movs byte), until cx = 0

        mov ah, 9 ;output - resultStr
        mov dx, resultStr
        int 21h

        mov dx, destStr ;output - copied string
        int 21h

        mov dx, byeStr ;output - byeStr
        int 21h

        mov ah, 7 ;wait for input
        int 21h

        ret

taskStr db "This program transfers bytes 10 to 15", NL, "Input string with length of 16:", NL , "$"
buffStr db 17, 0, 17 dup (?)
destStr db "******$"
resultStr db "Result string:", NL, "$"
byeStr db NL, "The program has now terminated.$"


org 100h

NL equ 0dh, 0ah

start:
        mov ah, 9 ;output task
        mov dx, taskStr
        int 21h

        mov ah, 1 ;echo one symbol input; output - ascii code of symbol in al
        int 21h
        xor ah, ah ;clear ah
        push ax ;save symbol code to stack

        mov ah, 9 ;output - findStr
        mov dx, findStr
        int 21h

        mov ah, 0ah ;input - string
        mov dx, buffStr
        int 21h

        cld ;direction - forward
        pop ax ;retrieve symbol code
        xor ch, ch ;clear ch
        mov cl, [buffStr + 1] ;amount of letters to cl
        add cl, 1 ;include last 0dh
        mov di, buffStr ;address of string...
        add di, 2 ;...starts here

next_:
        repne scasb ;repeat if not equal scasb (cmp al, di; inc di)
        jcxz result_ ;if it's here it's either: found a symbol or end of string; jcxz - jump if cx zero
        add ah, 1 ;amount of repetitioons
        jmp next_ ;next checks

result_:
        mov bl, ah ;answer to bl
        add bl, '0' ;convert to ascii

        mov ah, 9 ;output - resultStr
        mov dx, resultStr
        int 21h

        mov ah, 2 ;output - answer
        mov dl, bl
        int 21h

        mov ah, 9 ;output - byeStr
        mov dx, byeStr
        int 21h

        mov ah, 7 ;wait for input
        int 21h
        ret

taskStr db "This program finds how many times a symbol occurs in a string", NL, "Input symbol you want to find:", NL, "$"
findStr db NL, "Input string you will be looking in:", NL, "$"
buffStr db 10, 0, 10 dup (?)
resultStr db NL, "Result: $"
byeStr db NL, "The program has now terminated$"