Ensure that system environment variable PATH includes the location of all the compilers mentioned above.

Set the environment variable OBJECT_MODE to 64.

Download the source code of ICU version 4.2 for C from http://site.icu-project.org/download

At the shell prompt, execute the following commands:

gunzip -d < icu4c-4_2_1-AIX6_1-VA9.tgz | tar -xf - 
cd icu/source
./configure CC=/usr/vac/bin/cc CXX=/usr/vacpp/bin/xlc++ --disable-threads --disable-renaming 
gmake
gmake check 
gmake install

Set the environment variable LIBPATH to point to the location of ICU. AIX uses the environment variable LIBPATH to search for dynamically linked libraries.