A variable which represents an file to which a program has access. In Unix-related systems and languages, most processes start out with a few standard filehandles for user I/O, and get more by opening files.

In Unix, filehandles are implemented as "file descriptors", which are simply ints issued serially to a process by the kernel. In application C code, you're more likely to use FILE pointers (i.e. streams) as filehandles; these are a somewhat more stateful and easy-to-use wrapper around Unix file descriptors. C++'s iostream objects and Perl's filehandles are yet higher-level kinds of filehandle.