This function unlocks the supplied NDF (both the supplied identifier and the associated base NDF) so that another thread can then lock it for its own use using function ndfLock. After calling this function, an error will be reported if an attempt is made to access the NDF in any way, either through the supplied identifier or any other identifier that refers to the same base NDF. There are however two exceptions to this rule:

• An unlocked NDF identifier can be locked using ndfLock, allowing the thread full access to the NDF using the locked identifier.

• An unlocked NDF identifier can be annulled using ndfAnnul.

void ndfUnlock( int indf, int $\ast$status )

• This function returns without action if the NDF is already unlocked.

• This function will report an error if the supplied NDF is locked by any thread other than the currently running thread.

• The supplied NDF identifier will be removed from the NDF context associated with the currently running thread, and placed in a " null" context that is ignored by the ndfEnd function. The ndfReport function can be used to determine if any NDF identifiers are currently in this " null" context.

• This function attempts to execute even if " status" is set on entry, although no further error report will be made if it subsequently fails under these circumstances.

indf

$\ast$status