What is the EIO error?

Hi there,

I meet a problem when I try to get a character from keyboard in a subprocess
and end the
subprocess; I use gets or getc to read it,
part of code is as below:
if f==101 then



but I always get an error message: ERRNO:EIO. anyond can tell me what’s wrong
with my
code? And how to fix it? Or where I can find the description of error? Thanks,