ScaLAPACK

In ScaLAPACK, not unlike other library packages, a routine written and
compiled with fortran
is callable by a C program. On most systems, you will need to tag on an
underscore
at the end of the routine name when called. On IBM AIX, an underscore is
not required.
Other things to pay attention to are:
1) With fortran, matrix storage order is columwise while for C, it is
row-wise.
2) With fortran, variables - scalars or matrices - are passed by
reference. So,
when you call it from a C program, be sure to pass everything as
pointers,
even scalars.

The above are things you need to do when dealing with mix languages. It
has nothing
to do with ScaLAPACK, or any other library packages.