A method is provided that is executable by a processor of a computer. Note that the processor is communicatively coupled to a memory of the computer, and the memory stores a response block of a call command. In implementing the method, the processor defines a sub-functions field in the response block of the call command. Further the processor indicates that a set of functions of a set of instructions are installed and available at an interface based on a corresponding sub-functions flag within the sub-functions field being set. Note that the interface is also being executed on the computer and that the set of functions being represented by the corresponding sub-functions flag. The processor further indicates that the set of functions of the set of instructions are not installed based on the corresponding sub-functions flag not being set.