The following three elementary operations are defined on I-structures:
- allocate: reserves a specified number of elements for a new I-structure,
- I-fetch: retrieves the contents of the specified I-structure element (if the element has not yet been written, then this operation is automatically deferred),
- I-store: writes a value into the specified I-structure element (if that element is not empty, an error condition is reported).
These elementary operations are used to construct nodes SELECT and ASSIGN.
I-fetch instruction is implemented as split-phase memory operation:a read request issued to an I-structure is independent in time from the response received and thus does not cause a wait by the issuing PE.