VMS Language Features in Sun Fortran

This list is a summary of the VMS features that are included in f77. Details are elsewhere in this manual.

• Namelist I/O

• Unlabeled DO END DO

• Indefinite DO WHILE END DO

• BYTE data type

• Logical operations on integers, and arithmetic operations on logicals

• Additional field and edit descriptors for FORMAT statements:

  • Remaining characters (Q)

  • Carriage Control ($)

  • Octal (O)

  • Hexadecimal (X)

  • Hexadecimal (Z)

• Default field indicators for w, d, and e fields in FORMAT statements

• Reading into Hollerith edit descriptors

• APPEND option for OPEN

• Long names (32 characters)

• _ and $ in names

• Long source lines (132-character), if the -e option is on

• Records, structures, unions, and maps

• Getting addresses by the %LOC function

• Passing arguments by the %VAL function

• End-of-line comments

• OPTIONS statement

• VMS Tab-format source lines are valid.

• Initialize in common

  You can initialize variables in common blocks outside of BLOCK DATA subprograms. You can initialize portions of common blocks, but you cannot initialize portions of one common block in more than one subprogram.

• Radix-50

  Radix-50 constants are implemented as f77 bit-string constants, that is, no type is assumed.

• IMPLICIT NONE is treated as IMPLICIT UNDEFINED (A-Z)

• VIRTUAL is treated as DIMENSION.

• Initialize in declarations

  Initialization of variables in declaration statements is allowed. Example:

  ---

  	CHARACTER*10 NAME /'Nell'/ 

  ---

• Noncharacter format specifiers

  If a runtime format specifier is not of type CHARACTER, the compiler accepts that too, even though the FORTRAN Standard requires the CHARACTER type.

• Omitted arguments in subprogram calls

  The compiler accepts omitted actual argument in a subroutine call, that is, two consecutive commas compile to a null pointer. Reference to that dummy argument gives a segmentation fault.

• REAL*16

  (SPARC only) The compiler treats variables of type REAL*16 as quadruple precision.

• Noncharacter variables

  The FORTRAN Standard requires the FILE= specifier for OPEN and INQUIRE to be an expression of type CHARACTER. f77 accepts a numeric variable or array element reference.

• Consecutive operators

  f77 allows two consecutive arithmetic operators when the second operator is a unary + or -. Here are two consecutive operators:

  ---

  	X = A ** -B 

  ---

The above statement is treated as follows:

	X = A ** (-B) 

• Illegal real expressions

  When the compiler finds a REAL expression where it expects an integer expression, it truncates and makes a type conversion to INTEGER.

  Examples: Contexts for illegal real expressions that f77 converts to integer:

  • Alternate RETURN

  • Dimension declarators and array subscripts

  • Substring selectors

  • Computed GO TO

  • Logical unit number, record number, and record length

• Typeless numeric constants

  Binary, hexadecimal and octal constants are accepted in VMS form.

  Example: Constants-Binary (B), Octal (O), Hexadecimal (X or Z):

  ---

  	DATA N1 /B'0011111'/, N2/O'37'/, N3/X'1f'/, N4/Z'1f'/ 

  ---

• Function length on function name, rather than on the word FUNCTION

  The compiler accepts nonstandard length specifiers in function declarations.

  Example: Size on function name, rather than on the word FUNCTION:

  ---

  	INTEGER FUNCTION FCN*2 ( A, B, C ) 

  ---

• TYPE and ACCEPT statements are allowed.

• Alternate return

  The nonstandard & syntax for alternate-return actual arguments is treated as the standard FORTRAN * syntax. Example

  ---

  	CALL SUBX ( I, *100, Z
  )  ! Standard 
  	CALL SUBX ( I, &100, Z ) ! Nonstandard alternate syntax
  

  ---

  :

• The ENCODE and DECODE statements are accepted.

• Direct I/O with 'N record specifier

  The nonstandard record specifier 'N for direct-access I/O statements is accepted.

  Example: A nonstandard form for record specifier:

  ---

  	READ ( K ' N ) LIST 

  ---

  The above is treated as:

  ---

  	READ ( UNIT=K, REC=N ) LIST

  ---

  The logical unit number is K and the number of the record is N.

• NAME, RECORDSIZE, and TYPE options--OPEN has the following alternative options:

  • NAME is treated as FILE

  • RECORDSIZE is treated as RECL

  • TYPE is treated as STATUS

• DISPOSE=p

  The DISPOSE=p clause in the CLOSE statement is treated as STATUS=p.

• Special Intrinsics

  The compiler processes certain special intrinsic functions:

  • %VAL is accepted

  • %LOC is treated as LOC

  • %REF(expr) is treated as expr (with a warning if expris CHARACTER)

  • %DESCR is reported as an untranslatable feature

• Variable Expressions in FORMAT Statements

  In general, inside a FORMAT statement, any integer constant can be replaced by an arbitrary expression; the single exception is the n in an nH edit descriptor. The expression itself must be enclosed in angle brackets.

  Example: The 6 in the following statement is a constant:

  ---

  1 	FORMAT( 3F6.1 )

  ---

  6 can be replaced by the variable N, as in:

  ---

  1 	FORMAT( 3F<N>.1 ) 

  ---