Thanks guys for your help.
I have the next problem:
The example on how to use FCN with TMinuit
(http://root.cern.ch/root/html/examples/Ifit.C.html)
works only with the version 2.21/05 of root.
On a DEC/ALPHA/Unix4.0 the version 2.21/05 of
root needs the library libstdc++.so.2.9.0.0
Our informatician told me that this version
is not available in the moment.
(In our case we have libstdc++.so.2.8.1.1)
Florian Bauer