Allocatable Arrays

Fortran 90 allows arrays to be created on-the-fly; these are known as deferred-shape arrays:

• Declaration:

  INTEGER, DIMENSION(:), ALLOCATABLE :: ages   ! 1D
  REAL, DIMENSION(:,:), ALLOCATABLE :: speed   ! 2D

  Note ALLOCATABLE attribute and fixed rank.

• Allocation:

  READ*, isize
  ALLOCATE(ages(isize), STAT=ierr)
  IF (ierr /= 0) PRINT*, "ages : Allocation failed"
  
  ALLOCATE(speed(0:isize-1,10),STAT=ierr)
  IF (ierr /= 0) PRINT*, "speed : Allocation failed"

• 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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