In computing, an emulator is hardware or software that enables one computer system (called the host) to behave like another computer system (called the guest). An emulator typically enables the host system to run software or use peripheral devices designed for the guest system.
i.e. and e.g. are abbreviations of Latin phrases and each has its own specific meaning. i.e. stands for id est, meaning that is.. It is used to explain what exactly something means, or to say the same thing in other words. It is an abbreviation (Latin) of id est. Meaning that is.
p.r.n.: Abbreviation meaning when necessary (from the Latin  pro re nata, for an occasion that has arisen, as circumstances require, as needed).