A data structure of readily accessible units of memory is provided as computer useable media having computer readable program code logic providing information tables and a software emulation program to enable hardware to run new software that uses transactional memory and a bit associated with a transaction for executing transactional memory constructs. The data structure with Guest PTRAN bit is used in emulation of software written for a given computer on a different computer which executes a different set of instructions. The emulating instructions are used to provide transactional memory instructions on a computer which does not support those instructions natively.