In a set of registers, each individually addressable by register operations using a corresponding register identification, at least one register of the set of registers is an extended register having multiple storage locations. Values stored in the multiple storage locations are accessed, for example, according to the order in which they have been stored. Less than all of the multiple storage locations are accessible by a register operation at a given time. Older versions of software that do not recognize extended registers identify the extended register as having only one storage location. An extended register can be, for example, a stack register, a queue register, or a mixed register and values stored in the multiple storage locations are read and stored according to the characteristics of the register.