1"r" Opens a file for reading only.
2"r+" Opens a file for both reading and writing.
3"rb" Opens a file for reading only in binary format.
4"rb+" Opens a file for both reading and writing in binary format.
5"w" Opens a file for writing only.
6"a" Open for writing. The file is created if it does not exist.
7"a+" Open for reading and writing. The file is created if it does not exist.
8