1. A computer program product for executing a store instruction for storing data in an adapter, said computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: obtaining a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising: an opcode field identifying a store to adapter instruction; a first field identifying a first location that includes data to be stored in an adapter; a second field identifying a second location, the contents of which include a function handle identifying the adapter, a designation of an address space within the adapter in which data is to be stored, and an offset within the address space; and executing the machine instruction, the executing comprising: using the function handle to obtain a function table entry associated with the adapter; obtaining a data address of the adapter using at least one of information in the function table entry and the offset; and storing data from the first location in a specific location in the address space identified by the designation of the address space, the specific location identified by the data address of the adapter.