Per Bothner wrote most of the iostream library, but some portions
have their origins elsewhere in the free software community. Heinz
Seidl wrote the IO manipulators. The floating-point conversion software
is by David M. Gay of AT&T. Some code was derived from parts of BSD
4.4, which was written at the University of California, Berkeley.
The iostream classes are found in the libio library. An early
version was originally distributed in libg++, and they are still
included there as well, for convenience if you need other libg++
classes. Doug Lea was the original author of libg++, and some of
the file-management code still in libio is his.
Various people found bugs or offered suggestions. Hongjiu Lu worked hard to use the library as the default stdio implementation for Linux, and has provided much stress-testing of the library.