Newlib is a C standard library implementation intended for use on embedded systems. It is a conglomeration of several library parts, all under free software licenses that make them easily usable on embedded products.
It was created by Cygnus Support as part of building the first GNU cross-development toolchains. It is now maintained by Red Hat developer Jeff Johnston, and used in most commercial and non-commercial GCC ports for non-Linux embedded systems.
Read more about Newlib: System Calls, Inclusion