The advent of open systems standards, while beneficial, has not eliminated the diffi-culty of maintaining transporting large scale software systems across many varying platforms. this paper we discuss the need criteria for a effective porting strategy, one that allows the rapid inexpensive retargeting of large scale software systems to mâny widely varying platforms while not compromising the integrity of that software on any pieviously supported platform. Getting Tigger down, said Eeyore, and not hurting anybody, Keep those two ideas in your head, Piglet, you'll be all right.,' A. A. Milne, The World of Pooh, 1957, pp2L6, McCeltand & Stewart Ltd. A key component of any porting strategy is the methodology used to determine, represent, use, validate specifications of the target system's characteristics site or system dependent build run time controls. The standards efforts (e.g., pOSIX, ANSI C) are attempting to eliminate the large number of discrepancies that exist among systems today. However, the problem will always exist, for ieasons that are discussed. Hence, the main objective of this paper is to present justify the methodology that we use. _ Ihis methodology is in production use on several commercial products in Sietec. Its benefits include relieving the programmer from the burden of needing detailed knowledge of all the idiosyncrasies of the various target environments. It is suffi-ciently powerful tnat it accommodates many flavours of BSD, System V, DOS.
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