4
predicate, outputs TRUE if there are characters waiting to be
5
read from the read stream. If the read stream is a file, this
6
is equivalent to NOT EOFP. If the read stream is the terminal,
7
then echoing is turned off and the terminal is set to CBREAK
8
(character at a time instead of line at a time) mode. It
9
remains in this mode until some line-mode reading is requested
10
(e.g., READLIST). The Unix operating system forgets about any
11
pending characters when it switches modes, so the first KEYP
12
invocation will always output FALSE.