5_2

    org 100h

    NL_ equ 0dh, 0ah

start:
    mov ah, 9 ;output - helloStr
    mov dx, helloStr_
    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

helloStr_ 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: $"
byeStr_ db NL_, "The program has now terminated$"