An input channel for doing blocking reads from input sources like files and sockets.

An output channel for doing blocking writes to destinations like files and sockets.

Same as In_channel.stdin

Same as Out_channel.stdout

Same as Out_channel.stderr

Same as Out_channel.printf

Same as Out_channel.print_s

Same as Out_channel.eprint_s

Same as Out_channel.eprintf

Same as Out_channel.print_string

Same as Out_channel.print_endline

Same as Out_channel.prerr_endline