You open a stream explicitly by using the stream() function.

To explicitly open a file stream, use the open command. The advantage of opening file streams explicitly is that the program can determine that the stream open failed. The program can also have several separate streams for the same file.

If the file cannot be opened, a message is written to stderr. The I/O function returns as if the stream is empty, at end of file, and the file cannot be extended.

When a stream is explicitly opened, the stream() function returns a string that is the name of the stream. This is the only name that can be used to identify that stream. Multiple opens for the same path name open multiple streams, each with its own name.