Patent ID: 7689403

Claim:
In a data processing system in which the structure and operation of a target computer system is emulated by an emulation program on a host computer system and target system memory words, each having a number of bits that are stored within host system memory words, and wherein the number of bits in each of the target system memory words is less than the number of bits in each of the host system memory words, a process for providing target system program accessibility to complete host system memory words which enables newly defined target system functionality comprising the steps of: A) storing in host system memory target system words such that each target system word is contained within, but does not fill, a host system word, and B) aligning a plurality of target system words within the same plurality of host system words such that there is a region of normally utilized bits for containing each target system word within each of the plurality of host system words, and leaving within each of this plurality of host system words a remaining number of bits, and C) in response to a first target system instruction, invoking first newly defined target system functionality specified by the first target system instruction to be provided by the emulation program during emulation of the target system program by: 1) forming a first address of a first host system memory word, and 2) providing for reading by the target system program a first content of said first host system word including in the first content all of the bits of the first host system memory word, including those normally utilized and also those remaining bits within the first host system memory word, and D) in response to a second target system instruction invoking second newly defined target system functionality specified by the second target system instruction to be provided by the emulation program during emulation of a target system program by, 1) forming a second address of a second host system memory word, and 2) providing for writing by the target system program into all bits of the host system memory word including writing into both the normally utilized bits and also the remaining bits of the second host system memory word.