FORTRAN-10/20 and VAX FORTRAN Compatibility Manual

This "FORTRAN-10/20 and VAX FORTRAN Compatibility Manual" (Order Number AA-Y868C-TK, February 1987) describes the similarities and differences between FORTRAN-10/20 (Version 11, running on TOPS-10 V7.03 and TOPS-20 V4.1/V6.1) and VAX FORTRAN (Version 4.5, running on VAX/VMS V4.5). It is intended for users migrating FORTRAN programs between DECsystem-10/20 and VAX computers.

The document highlights:

• Extensions: Features common to both FORTRAN versions that extend the FORTRAN-77 standard, including enhanced comment types, longer identifiers, support for INCLUDE statements, alternate floating-point formats, and advanced array equivalencing.
• Incompatibilities: Detailed differences between the two FORTRAN implementations in areas such as program format (e.g., tab character interpretation, source line length), argument passing mechanisms (value-result vs. reference), logical test evaluations, and the behavior of various I/O statements (OPEN, CLOSE, DECODE, ENCODE, NAMELIST). It also covers distinctions in FORTRAN-supplied subprograms and intrinsic functions.
• Limits: Comparisons of compiler-imposed software limitations (e.g., number of nested DO loops, character string lengths) and maximum record lengths. It also explains the hardware representation and implications of different FORTRAN data types (INTEGER, LOGICAL, CHARACTER, Floating-Point) on the respective systems, including various floating-point number formats (F-, D-, G-, H-floating).