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Future developments in molecular electronicsi-b not only offer the possibility of high density archival memories, 1015 to 1018 gates/cc, but also new routes to fabrication of high levels of parallel processors (> 106) and hence to new computer architectures. A central theme of molecular electronics is that information can be stored as conformational changes in chemical moieties or functional groups. Further, these functional units are chosen or designed so that their structure facilitates the storage of information via reversible conformational changes, either in bond distances or in bond angles, or both. In exploring possible switching and information storage mechanisms at the molecular-size level, it has become apparent that there are many analogues or alternatives possible for any logical function which might be desired. It is even more exciting to realize that some structural chemical units or configurations offer completely new functional or logical capabilities. The example offered below is the molecular analogue of the CASE statement in PASCAL (proposed by an NRL summer student employee7). As suggested in the title, one of the purposes of this article is to enhance the appreciation of the universality of the 'chemical' or 'molecular' systems to express logical functions. The literature on molecular electronic concepts is growing and some reviews are available1-4. Two Molecular Electronic Device (MED) workshops5-6 have been held in Washington, D.C. (1981 and 1983) and an International Symposium on Bioelectric and Molecular Electronic Devices 8 was held in Tokyo, 20-21 November 1985. Beyond the strong interest current in Japan9, interest is also developing in England and Soviet block11.
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