The register machine has, for a memory external to its finite-state machinean unbounded (cf: footnote|countable and unbounded) collection of discrete and uniquely labelled locations with "unbounded" capacity, called "registers". These registers hold only natural numbers (zero and the positive integers). Per a list of sequential instructions in the finite state machine's TABLE, a few (e.g. 2) types of primitive operations operate on the contents of these "registers". Finally, a "conditional-expression" in the form of an "IF-THEN-ELSE" is available to test the contents of one or two registers and "branch/jump" the finite state machine out of the default instruction-sequence.