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What's the difference between fortran 77 and fortran 90?


Asked by Byron Harris on Dec 03, 2021 FAQ



Fortran 90 is a superset of Fortran 77, that is programs written in Fortran 77 may be compiled and run as Fortran 90 programs. However Fortran 90 is more than a new release of Fortran 77. The Fortran 90 standard introduces many new facilities for array type operations, new methods for specifying precision, free form, recursion, dynamic arrays etc.
Furthermore,
Fortran 90 for the Fortran 77 Programmer. This tutorial is written in order to ease the transition from the very common and popular programming language Fortran 77 to the more modern Fortran 90. This transition uses the fact that Fortran 77 is a pure subset of Fortran 90.
Besides, Fortran encompasses a lineage of versions, each of which evolved to add extensions to the language while usually retaining compatibility with prior versions. Successive versions have added support for structured programming and processing of character-based data (FORTRAN 77), array programming, modular programming...
And,
This is free-form temp = x; x = y; y = temp ! Swap x and y write(6,*) 'x and y are =', & x,y ! Print x and y visiblespaces=false For back-compatibility with Fortran 77, Fortran 90 accepts a ``fixed source form''. In short, the fixed source form requirements are:
Just so,
The names of earlier versions of the language through FORTRAN 77 were conventionally spelled in all-capitals (FORTRAN 77 was the last version in which the use of lowercase letters in keywords was strictly non-standard). The capitalization has been dropped in referring to newer versions beginning with Fortran 90.