Language Obsolescence

 

Fortran 90 has carried forward the whole of FORTRAN 77 and also a number of features from existing Fortran compilers. This has been done to protect the investment in the millions of lines of code that have been written in Fortran since it was first developed. Inevitably, as modern features have been added, many of the older features have become redundant and programmers, especially those using Fortran 90 for the first time, need to be aware of the possible pit-falls in using them.

Fortran 90 has a number of features marked as obsolescent, this means,

• they are already redundant in FORTRAN 77;
• better methods of programming already existed in the FORTRAN 77 standard;
• programmers should stop using them;
• the standards committee's intention is that many of these features will be removed from the next revision of the language, Fortran 95;

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• Obsolescent Features
  • Arithmetic IF Statement
  • ASSIGN Statement
  • ASSIGN ed GOTO Statement
  • ASSIGN ed FORMAT Statement
  • Hollerith Format Strings
  • PAUSE Statement
  • REAL and DOUBLE PRECISION DO-loop Variables
  • Shared DO-loop Termination
  • Alternate RETURN
  • Branching to an END IF
• Undesirable Features
  • Fixed Source Form
  • Implicit Declaration of Variables
  • COMMON Blocks
  • Assumed Size Arrays
  • EQUIVALENCE Statement
  • ENTRY Statement