### 5.1.4.3 Assumed-Size Specifications

An assumed-size array is a dummy argument array that assumes the size (only) of its associated actual argument array; the rank and extents can differ for the actual and dummy arrays. An assumed-size specification takes the following form:

  ([expli-shape-spec,] [expli-shape-spec,]... [dl:] *)
  expli-shape-spec
  Is an explicit-shape specification (see Section 5.1.4.1).
  dl
  Is a specification expression indicating the lower bound of the dimension. The expression can have a positive, negative, or zero value. If necessary, the value is converted to integer type.

  If the lower bound is not specified, it is assumed to be 1.

  *
  Is the upper bound of the last dimension.

The rank of the array is the number of explicit-shape specifications plus 1.

The size of the array is assumed from the actual argument associated with the assumed-size dummy array as follows:

- If the actual argument is an array of type other than default character, the size of the dummy array is the size of the actual array.
- If the actual argument is an array element of type other than default character, the size of the dummy array is `a + 1 - s` , where s is the subscript order value and a is the size of the actual array.
- If the actual argument is a default character array, array element, or array element substring, and it begins at character storage unit b of an array with n character storage units, the size of the dummy array is as follows:

              MAX(INT((n + 1 - b)/y), 0)

  The y is the length of an element of the dummy array.

An assumed-size array can only be used as a whole array reference in the following cases:

- When it is an actual argument in a procedure reference that does not require the shape
- In the intrinsic function LBOUND

Because the actual size of an assumed-size array is unknown, an assumed-size array cannot be used as any of the following in an I/O statement:

- An array name in the I/O list
- A unit identifier for an internal file
- A run-time format specifier

The following is an example of an assumed-size specification:

    SUBROUTINE SUB(A, N)
      REAL A, N
      DIMENSION A(1:N, *)
      ...

For More Information:

For details on array element order, see Section 3.4.2.2.

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