Computing Profession
Advertisement
Reduction in the size of decision tables can be accomplished by several techniques. The techniques considered in this paper are on the parsing of decision tables with regard to horizontal and vertical data structures, job identity, hardware and job priorities, and context relationships. Such parsing rests upon some conventions for the linkage of decision tables.
A comparison of batch processing and instant turnaround
A study of the programming efforts of students in an introductory programming course is presented and the effects of having instant turnaround (a few minutes) as opposed to conventional batch processing with turnaround times of a few hours are examined. Among the items compared are the number of computer runs per trip to the computation center, program preparation time, keypunching time, debugging time, number of runs, and elapsed time from the first run to the last run on each problem. Even though the results are influenced by the fact that “bonus points” were given for completion of a programming problem in less than a specified number of runs, there is evidence to support “Instant” over “Batch”.
The most fundamental underlying problem in sophisticated software systems involving elaborate, changing data structure is dynamic storage allocation for flexible problem modeling. The Free Storage Package of the AED-1 Compiler System allows blocks of available storage to be obtained and returned for reuse. The total available space is partitioned into a hierarchy of free storage zones, each of which has its own characteristics. Blocks may be of any size, and special provisions allow efficient handling of selected sizes, control of shattering and garbage collection, and sharing of physical space between zones. The routines of the package perform high level functions automatically, but also allow access and control of fine internal details as well.
ARPA: a visible means of support
The Advanced Research Projects Agency has probably done more to lift computer science from other disciplines and to put it on its own feet than any organization inside or outside of government. Even today, when support of computing is spread throughout the government, ARPA is practically alone in its belief that computing deserves to be a separate discipline. Ironically, the computer profession knows little about this friendly benefactor.
Description of basic algorithm DETAB/65 preprocessor
The basic algorithm for the conversion of decision tables into COBOL code is contained in the generator portion of the DETAB/65 preprocessor. The generator analyzes a decision table and produces simple COBOL conditional statements. Core storage is saved by using queueing techniques and extensive indexing and also by outputting the code as it is generated, a line at a time. The only optimization attempted is the elimination of obviously unnecessary tests on certain conditions in the decision table.
Since the preprocessor and this language associated with it were developed for COBOL users, the preprocessor was written in a modular form in required COBOL-61.
A user-oriented time-shared online system
An existing system and planned additions within the Data Processing Laboratory of the Brain Research Institute at UCLA is described. The system represents an attempt to provide research workers of the Institute with the ability to interact directly with a highly sophisticated digital computing complex in the most direct and simple fashion possible. It is anticipated that, with the accumulation of experience using the present system, significant advances will be possible in the system design through determination of interface parameters between the biological scientist and the digital computer.
A language independent macro processor
The problem of obtaining starting values for the Newton-Raphson calculation of √x on a digital computer is considered. It is shown that the conventionally used best uniform approximations to √x do not provide optimal starting values. The problem of obtaining optimal starting values is stated, and several basic results are proved. A table of optimal polynomial starting values is given.
The internal organization of string processing systems is discussed. Six techniques for data structures are presented and evaluated on the basis of: (1) creation of strings; (2) examination of strings; and (3) alteration of strings. Speed of operation, storage requirements, effect on paging, and programmer convenience are also considered. One of the techniques, single-word linked blocks, is used in an example demonstrating an implementation of a SNOBOL string processing language on an IBM System/360.
Changes in government procurement policies
Several years ago there was an attempt in Washington to place the selection of government computers in a central, highly placed office. Individual government agencies, led by the Department of Defense, successfully beat back this attempt. Today, two years later, it looks as though other forms of centralization are being worked into the government fabric at lower levels, one in the Department of Defense, another in the General Services Administration.
Implementing phrase-structure productions in PL/I
A method is described for implementing the productions of a context-free phrase structure grammar in a PL/I procedure whose structure and statements parallel the structure and notation of the grammar.
The simulation of time sharing systems
The development of new large scale time-sharing systems has raised a number of problems for computation center management. Not only is it necessary to develop an appropriate hardware configuration for these systems, but appropriate software adjustments must be made. Unfortunately, these systems often do not respond to changes in the manner that intuition would suggest, and there are few guides to assist in the analysis of performance characteristics. The development of a comprehensive simulation model to assist in the investigation of these questions is described in this paper. The resulting model has a general purpose design and can be used to study a variety of time-sharing systems. It can also be used to assist in the design and development of new time-sharing algorithms or techniques. For the sake of efficiency and greater applicability, the model was implemented in a limited FORTRAN subset that is compatible with most FORTRAN IV compilers. The use of the simulation is demonstrated by a study of the IBM 360/67 time-sharing system.
Shape the Future of Computing
ACM encourages its members to take a direct hand in shaping the future of the association. There are more ways than ever to get involved.
Get InvolvedCommunications of the ACM (CACM) is now a fully Open Access publication.
By opening CACM to the world, we hope to increase engagement among the broader computer science community and encourage non-members to discover the rich resources ACM has to offer.
Learn More