### 15.2.4.5 INSTANCE Directive (TU*X only)

The INSTANCE directive specifies the availability of named common blocks. It takes the following form:

  c$PAR INSTANCE { SINGLE | PARALLEL } /cb/[, /cb/] ...
  c
  Is one of the following: C (or c), !, or * (see Section 15.2.1).
  cb
  Is the name of the common block. The slashes are required.

Rules and Behavior

The specifications are described as follows:

- SINGLE - Specifies that there will be a single instance of the named common blocks. This implies that all threads share the same copy, and assignments to the constituent items in the common blocks occurring in one thread affect the values of those items in the same named common blocks in other threads.
- PARALLEL - This is the same as specifying the OpenMP Fortran API THREADPRIVATE directive (see Section 15.2.3.14).

INSTANCE SINGLE is the default for named common blocks.

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