[Crespyl]

When not given a file, cat will just read from stdin, so you can use "cat > file.c", write some text, and send EOF with ^D when you're done.

Obviously, there's no way to go back and edit anything mid-stream, you have to write the whole thing out in one shot.

[Koshkin]

The backspace does work within the line.

[exikyut]

If your terminal is in line-buffered mode.