The routine determines whether a specified type of access to an NDF is available, or whether it has been disabled. If access is not available, then any attempt to access the NDF in this way will fail.

CALL NDF_ISACC( INDF, ACCESS, ISACC, STATUS )

INDF = INTEGER (Given)

ACCESS = CHARACTER $\ast$ ( $\ast$ ) (Given)

ISACC = LOGICAL (Returned)

STATUS = INTEGER (Given and Returned)

The valid access types control the following operations on the NDF:

• ’BOUNDS’ permits the pixel-index bounds of a base NDF to be altered.

• ’DELETE’ permits deletion of the NDF.

• ’SHIFT’ permits pixel-index shifts to be applied to a base NDF.

• ’TYPE’ permits the data types of an NDF’s components to be altered.

• ’WRITE’ permits new values to be written to the NDF, and the state of any of its components to be reset.