Exactly, when you don't specify the f option it automatically will go to the default device. An example is if I don't use the f it will go to my default device which is my tape drive. I'm assuming that probably is trying to write to your floppy drive or where it should be.
Originally posted by sverre It means you didn't give it the f flag. Normally an extraction command should look like this (v is for verbose and is optional):