The recent demonstration of an all-optical, stored-program, digital computer by our group focused on high-speed optoelectronic design. It was made possible by a new digital design method known as time-of-flight design. A rudimentary, but general-purpose, proof of principle computer was built, which is all-optical in the sense that all signals connecting logic gates and all memory are optical in nature. LiNbO/sub 3/ directional couplers, electrooptic switches, are used to perform logic operations. In addition to demonstrating stored program operation in an optoelectronic digital computer, the system demonstrated the feasibility of the new design method, which does nor use any flip-flops or other bistable devices for synchronization or memory. This potentially allows system clock rates of the same order as device bandwidth. This paper describes how the time-of-flight design method was motivated by the special properties of optoelectronic digital design. The basic principles of the method we employed will be discussed along with some of its potential advantages. The experimental work with digital optical circuits leading up to and including the stored program computer experiment will then be discussed. Finally, the future potential of time-of-flight design in high-bandwidth optoelectronic systems will be discussed.>

Abstract One of the difficult problems that faces a compiler writer is to devise a grammar that is suitable for both efficient parsing and semantic attribution. This paper describes a system that resolves conflicts in LR(1) parsing by taking advantage of information in the parse tree. The system, which functions as part of a compiler generator, rewrites the user's grammar to remove parsing conflicts. It then places code into the generated compiler that rewrites the parse tree during parsing so as to produce the tree of the original grammar. The compiler writer can then write the semantic attribution to fit his or her original grammar without any knowledge of the changes made. The method is expected to be efficient in most cases, even in parsing systems that do not explicitly build the entire parse tree. The method complements previous work in its capabilities and advantages. The system has been implemented and integrated into a compiler generator system.

This paper describes a technique for time multi­ plexing multiple processors on a single hardware plat­ rorm. This technique should be useful whenever an archi­ tecture employs devices that have high bandwidth and simultaneously high temporal latency. These architec­ tures were explored during the development of a bit serial optical computer using optical fibers for interconnection and directional couplers as logic devices. We describe an optical counter developed in our laboratory as a proof­ ?f-principle experiment that permits two simultaneous, mdependent counts to be accumulated on the same hardware. Future machines may be envisioned imple­ menting hundreds to thousands of processors running on one optical computer.

A data format for context-free grammar representation called COMAR is proposed. It is intended to be used for integration and communication of various tools operating on CFGs, e.g. language-invariant grammar transformations, analysis of grammar properties, and parser generation. A compact ASCII file representation for COMAR is defined to be used as an interface language for such tools. Routines necessary for tool development based on COMAR are available: a front end producing COMAR representation from EBNF text, a set of I/O routines, and a set of functions constructing and accessing a Comar data structure in memory.