FORTRAN vs. C

[shepard-: at :-dirac.tcg.anl.gov (Ron Shepard)]

For programmers interested in converting existing FORTRAN programs to
 C, there is a book entitled "From Fortran to C" by J. F. Kerrigan ISBN
 0-8306-7661-9, which contains some useful information.  It is
 organized by Fortran keyword, and in each section gives a C
 replacement for the Fortran construct.
 I cannot really recommend the book as a reference for going the other
 way, (i.e. for C programmers learning about Fortran) because most of
 the Fortran examples are not particularly well written.  For example,
     (1) most of the format statements have hollerith strings in them
 (instead of the conceptually simpler, consistent, use of '-delimited
 character strings),
     (2) variables in common blocks are initialized in data statements
 (in f77 such initializations must be localized in block data
 subprograms),
     (3) named common blocks appear inconsistently in save statements
 (in f77 if a block is saved anywhere, it must be saved everywhere),
 and
     (4) the examples use fortran specific intrinsic functions (a bad
 programming practice; generic intrinsics should always be used when
 possible to enhance portability).
 Another general shortcoming of the book, particularly for scientific
 programmers, is that all of the correspondences between Fortran and C
 data types are based on a 16-bit microcomputer point of view.  For
 example, C types "double" and "long double" are both mapped
 to Fortran
 "double precision" which in turn is associated in the text with
 "real*8".  (No mention is made of fortran "real*16" which is
 supported
 on many machines as 128-bit floating point.)  However, I think on a
 Cray, a C "double" maps to "real", which is really
 equivalent to
 either of the fortran declarations "real*4" or "real*8", and
 C "long
 double" maps to "double precision", which is really equivalent to
 "real*16".  Maybe someone with more C experience on a Cray can correct
 this if I'm wrong.
 There is also some confusion introduced in the book when C "char" is
 identified with Fortran "character".  In fact, the C "char"
 data type
 is really an integer data type.  A better correspondence would be C
 "char" with the result of the fortran intrinsic ichar() operating on a
 character*1 argument.  Character variables in Fortran are really
 structured entities, with the components of the structure hidden from
 the programmer (until cross-language calls are needed, at which time
 the actual structure must be dealt with explicitly).  This applies to
 fortran character values of any length, whereas in C long strings are
 associated with char arrays.
 As far as I know, this is the only book available that is devoted to
 bridging the Fortran to C language gap.
 -ron shepard
 p.s. I know that nonprogrammers on this bboard may be getting bored
 with this discussion, but as long as useful information is being
 exchanged, I'm reluctant to encourage its termination. Bear with us
 and you'll eventually benefit from the superior code that we write.  (:-)