Patent ID: 7653527

Claim:
An Apparatus for emulating in software on a host system, operations of a target computer system including: A) a central processing unit which is a first part of the host system; B) a host system main memory which is a part of a second part of the host system; C) target system memory contained within said host system main memory; D) an emulation program stored within the host system main memory, the emulation program comprising host system machine instructions for processing by the host system central processing unit, the emulation program including a plurality of software modules, and the plurality of software modules including a set of selectable alternative software modules, being simultaneously resident in the host system main memory; E) an option control for selection of a plurality of options by a user which have influence upon the operation of the emulation program; and, F) said selection made by the option control in response to a selection of a user chosen specific software module, the selection controlling branching by the emulation program and resulting in the emulation program utilizing the user chosen specific software module during the emulating of the operations of the target computer system.