A .doc file is a Microsoft Word file.
Since you’re in Russia, reminds me of long ago in a youth hostel in Europe. Couple of Russian guys at the other end of the table had possession of a pot of either tea or coffee. I asked them if it was tea or coffee.
“Yes,” one replied.
No, I said, is it tea OR coffee?
“Yes,” he replied again with a smile.
When I tasted it, I considered that a pretty accurate answer.