Allocatable Arrays

Fortran 90 allows arrays to be created on-the-fly; these are known as deferred-shape arrays and use dynamic heap storage.

Deferred-shape arrays are:

• declared like explicit-shape arrays but without the extents and with the ALLOCATABLE attribute:

      INTEGER, DIMENSION(:), ALLOCATABLE :: ages
      REAL, DIMENSION(:,:), ALLOCATABLE :: speed

• given a size in an ALLOCATE statement which assigns an area of memory to the object:

      ALLOCATE(ages(1:10), STAT=ierr)
      ALLOCATE(speed(-lwb:upb,-50:0),STAT=ierr)

• the optional STAT= field reports on the success of the storage request. If the INTEGER variable ierr is zero the request was successful otherwise it failed.

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