объясни этот код для нахождения crc : from tkinter import *
from tkinter import ttk
from tkinter import filedialog
from tkinter import Tk, Label
from PIL import ImageTk, Image
import os

def crc():
    try:
        filename = entry.get()
        divisor = entry2.get()
        seqnumber = 0
        frame_count = 0  # Counter for converted frames
        with open(filename, "rb") as file:
            while True:
                seqnumber += 1
                sqn = bin(seqnumber)[2:].zfill(16)
                data_txt = file.read(1024)
                if not data_txt:
                    break
                div = "".join(map("{:08b}".format, data_txt))
                divident = div
                while len(divident) >= len(divisor):
                    rez = ''
                    bb = divident[:len(divisor)]
                    divident = divident[len(divisor):]
                    f = 0
                    for i in range(0, len(divisor)):
                        if bb[i] != divisor[i]:
                            f = 1
                            rez += '1'
                        if bb[i] == divisor[i] and f == 1:
                            rez += '0'
                    divident = rez + divident
                crc = divident.zfill(16)
                address = bin(id(file))[2:].zfill(16)
                frame = sqn + address + div + crc
                with open("frame.txt", "a") as file2:
                    file2.write(frame)
                frame_count += 1  # Increment the frame counter
        label3.config(text="Файл сконвертирован и записан!")
        label5.config(text=f"Количество отправленных пакетов: {frame_count}")
    except FileNotFoundError:
        label3.config(text="Ошибка: Файл не найден!")
    except IOError:
        label3.config(text="Ошибка: Не удалось прочитать файл!")
    except Exception as e:
        label3.config(text=f"Ошибка: {str(e)}")

def choose_file():
    try:
        filename = filedialog.askopenfilename()
        entry.delete(0, END)
        entry.insert(0, filename)
        file_size = os.path.getsize(filename)
        label4.config(text=f"Вес файла: {file_size} байт")
    except FileNotFoundError:
        label4.config(text="Ошибка: Файл не найден!")
    except Exception as e:
        label4.config(text=f"Ошибка: {str(e)}")

def calculate_crc():
    label1.pack()
    entry.pack()
    btn_choose.pack()
    label4.pack()
    label2.pack()
    entry2.pack()
    btn1.pack()
    label3.pack()
    label5.pack()

def show_calculate_crc():
    label20.pack_forget()
    label21.pack_forget()
    btn20.pack_forget()
    label1.pack()
    entry.pack()
    btn_choose.pack()
    label4.pack()
    label2.pack()
    entry2.pack()
    btn1.pack()
    label3.pack()
    label5.pack()

def show_check_file():
    label1.pack_forget()
    entry.pack_forget()
    btn_choose.pack_forget()
    label4.pack_forget()
    label2.pack_forget()
    entry2.pack_forget()
    btn1.pack_forget()
    label3.pack_forget()
    label5.pack_forget()
    btn20.pack()

def chekkk():
    divisor = "11000101110110111"
    with open("frame.txt", "r") as file3:
        while True:
            seqnumber = file3.read(16)
            if not seqnumber:
                break
            address = file3.read(16)
            data_byte = file3.read(1024)
            if len(data_byte) < 1024:
                file3.seek(24)
                data_byte = file3.read(len(data_byte) - 16)
            crc = file3.read(16)
            divident = data_byte
            while len(divident) >= len(divisor):
                rez = ''
                bb = divident[:len(divisor)]
                divident = divident[len(divisor):]
                f = 0
                for i in range(0, len(divisor)):
                    if bb[i] != divisor[i]:
                        f = 1
                        rez += '1'
                    if bb[i] == divisor[i] and f == 1:
                        rez += '0'
                divident = rez + divident
            crc_new = divident.zfill(16)
            if crc_new == crc:
                label20.pack()
            else:
                label21.pack()

root = Tk()
root.title("CRC Calculator")
root.geometry("400x265")
root.resizable(False, False)

style = ttk.Style()
style.configure("TLabel", font=("Arial", 12))
style.configure("TButton", font=("Arial", 12), background="lime green")

icon = ImageTk.PhotoImage(file="icon.png")
root.iconphoto(False, icon)

background_image = ImageTk.PhotoImage(Image.open("vvv.jpg"))
background_label = Label(root, image=background_image)
background_label.place(x=0, y=0, relwidth=1, relheight=1)

label1 = ttk.Label(text="Напишите название файла:", font=("Arial", 12, "bold"))
entry = ttk.Entry(font=("Arial", 12))
btn_choose = ttk.Button(text="Выбрать файл", command=choose_file)
label4 = ttk.Label(text="")
label2 = ttk.Label(text="Введите полином:", font=("Arial", 12, "bold"))
entry2 = ttk.Entry(font=("Arial", 12))
btn1 = ttk.Button(text="Вычислить CRC и отправить", command=crc)
label3 = ttk.Label(text="")
label5 = ttk.Label(text="")
btn_choose = ttk.Button(text="Выбрать файл", command=choose_file)

btn20 = ttk.Button(text="Выполнить проверку", command=chekkk)
label20 = ttk.Label(text="Проверка прошла успешно", font=("Arial", 12, "bold"))
label21 = ttk.Label(text="Проверка провалена", font=("Arial", 12, "bold"))

menu = Menu(root)
root.config(menu=menu)

options_menu = Menu(menu)
menu.add_cascade(label="Options", menu=options_menu)

options_menu.add_command(label="Вычислить CRC", command=show_calculate_crc)
options_menu.add_command(label="Проверить файл", command=show_check_file)

root.mainloop()