Here is a list of all files with brief descriptions:

doc.hh
ipopt-common.hh
ipopt-common.hxx
ipopt-parameters-updater.hh
ipopt-sparse.cc
ipopt-sparse.hh
ipopt-td.cc
ipopt-td.hh
ipopt.cc
ipopt.hh
tnlp.cc
tnlp.hh
tnlp.hxx