July 1965 - Vol. 8 No. 7
Features
The structure of yet another ALGOL compiler
A high-speed “top down” method of syntax analysis which completely eliminates “back-up” of the source string has been implemented in a convenient macro-language. A technique of simulation at compile time of the use of a conventional run-time stack enables the generation of code for expressions which minimizes stores, fetches and stack-pointer motion at run time, while properly treating recursion and side effects of procedures. Block structure and recursion are handled without need for interpretive methods at run time. The “context problem” in the transmission to recursive procedures of parameters “called by name” is solved in a manner which permits the handling of the common cases of simple expressions and array identifiers with particular efficiency.
This paper is intended as an outline of the various conventions which are being considered for the use of flowchart symbols in the preparation of all types of flowcharts for information processing systems. The conventions are applied to the use of the symbols appearing in the proposed American Standard Flowchart Symbols for Information Processing Systems. This paper is concerned with the use of the proposed American Standard Flowchart Symbols and not with the symbols per se.
Redundant instructions may be discarded during the final stage of compilation by using a simple optimizing technique called peephole optimization. The method is described and examples are given.
Method for hyphenating at the end of a printed line
A description of a method of hyphenation is presented as a result of application of several general rules. The character sets considered by the routine and the method are briefly outlined.
The organization of structured files
A data file is an integral part of a data processing system. In many systems, the selection of an organization for the data within the file can be critical to the system's operating efficiency.
This paper provides the systems designer with an information source which describes ten techniques that may be employed for organizing structured data.
The characteristics of the organizations described are application independent, thus providing the designer with a reference which allows him to limit the number of file organizations he must consider for his system.
The predictive analyzer and a path elimination technique
Some of the characteristic features of a predictive analyzer, a system of syntactic analysis now operational at Harvard on an IBM 7094, are delineated. The advantages and disadvantages of the system are discussed in comparison to those of an immediate constituent analyzer, developed at the RAND Corporation with Robinson's English grammar. In addition, a new technique is described for repetitive path elimination for a predictive analyzer, which can now claim efficiency both in processing time and core storage requirement.
Determining a computing center environment
An investigation is described in which several generally unavailable parameters descriptive of a computing center environment are obtained. The actual data collection and reduction is described, and the results of one month of this collection are tabulated and summarized.
