FindChar_1 PROC
    MOV ESI, OFFSET DataString  ; load offset of variable 'DataString' into reg. ESI
    MOV AL, 'J'         ; load the code of character 'J' into reg. AH
Check_End:
    CMP BYTE PTR [ESI], 0FFFFH  ; is it the end of a string (special character FF)?
    JE Not_Find         ; found end character (guard)
    CMP AH, [ESI]           ; compare a char. with 1 char of string 'DataString'
    JE Got_Equal            ; character found!
    ADD ESI, 1          ; increment an offset
    JMP Check_End           ; search loop
Got_Equal:
    MOV DL, [ESI]           ; load found char into DL
    JMP Done
Not_Find:
    MOV EAX,0               ; character not found
    RET             ; return from procedure
Done:
    MOV EAX,1