dd is a "stream duplicator".
dd with no operands means it will be reading and writing to the standard input/output (keyboard and screen).
From the man page (
The dd utility copies the standard input to the standard output.
So, issuing the command
dd and then sending a break ControlC results in nothing being input, and nothing being written. Until you sent the break,
dd was waiting for input.
Here are some examples (press ControlD to tell
dd you are done entering text)
0+1 records in
0+1 records out
13 bytes transferred in 6.140313 secs (2 bytes/sec)
To convert from regular to upper/lowercase:
$ dd conv=ucase