File Mode Properties of the I/O Stream
r Read-only.
r+ Both reading and writing are allowed.
w Write-only. A new file is created (or an old one overwritten as if new).
w+ Both reading and writing are allowed, but File.new creates a new file from scratch (or overwrites an old one as if new).
a Write (in append mode).
a+ Both reading and writing are allowed (in append mode). The file pointer is placed at the end of the file and writes will make the file longer.
b Binary file mode (only required on Windows). You can use it in conjunction with any of the other modes listed.