STOD 1L "12 May 1992"

Table of contents


stod - convert Fortran program from single-precision to double-precision


stod < infile >outfile

stod copies its standard input to standard output, converting Fortran single-precision constants, built-in functions, and type declarations to double precision.

Floating-point FORMAT specifications are left intact; on some ancient systems, they may require modifications. They do not under the rules of Fortran 77.

Leading tabs are correctly interpreted according to common extended Fortran rules.

stod recognizes all of the standard Fortran 77 single- and double-precision functions, as well as the pair rand/drand (UNIX pseudo-random number generators), and the pair r1mach/d1mach from the PORT library framework.

stod's other purpose is to demonstrate a modest lex(1) program.


Undeclared variables are not type-converted. To find such instances, use the Extended PFORT Verifier, pfort(1), or the Fortran checker, ftnchek(1). Some UNIX Fortran compilers have a compile-time option, usually called -u, to flag undeclared variables.

Text beyond column 72 is discarded when lines are collected into Fortran statements.

stod does not handle embedded ASCII tab characters correctly when long lines are to be broken. A Fortran-sensitive detabbing utility should be applied first if the input file possibly contains embedded tabs. Note that expand(1) cannot be used to do this job correctly!

Mixed-precision code may not be converted correctly. For example, SNGL(DFLOAT(N)) will become DBLE(DFLOAT(N)), which is syntactically incorrect.

Functions and variables of type COMPLEX are not converted, because Fortran 77 does not define a double precision complex type. Complex constants will be converted, however, since their real and imaginary parts look like normal floating-point values.


dtos(1), ftnchek(1), lex(1), pfort(1).


Nelson H. F. Beebe, Ph.D.

Center for Scientific Computing

Department of Mathematics

South Physics Building

University of Utah

Salt Lake City, UT 84112

Tel: (801) 581-5254

FAX: (801) 581-4148

Email: <>