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/GNU Fortran 7

6.1.2 Old-style variable initialization

GNU Fortran allows old-style initialization of variables of the form:

INTEGER i/1/,j/2/
REAL x(2,2) /3*0.,1./

The syntax for the initializers is as for the DATA statement, but unlike in a DATA statement, an initializer only applies to the variable immediately preceding the initialization. In other words, something like INTEGER I,J/2,3/ is not valid. This style of initialization is only allowed in declarations without double colons (::); the double colons were introduced in Fortran 90, which also introduced a standard syntax for initializing variables in type declarations.

Examples of standard-conforming code equivalent to the above example are:

! Fortran 90
      INTEGER :: i = 1, j = 2
      REAL :: x(2,2) = RESHAPE((/0.,0.,0.,1./),SHAPE(x))
! Fortran 77
      INTEGER i, j
      REAL x(2,2)
      DATA i/1/, j/2/, x/3*0.,1./

Note that variables which are explicitly initialized in declarations or in DATA statements automatically acquire the SAVE attribute.

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https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gfortran/Old_002dstyle-variable-initialization.html