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Research and Advances

A note on reliable full-duplex transmission over half-duplex links

A simple procedure for achieving reliable full-duplex transmission over half-duplex links is proposed. The scheme is compared with another of the same type, which has recently been described in the literature. Finally, some comments are made on another group of related transmission procedures which have been shown to be unreliable under some circumstances.
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Research and Advances

Clarification of Fortran standards—initial progress

In 1966, after four years of effort, FORTRAN became the first programming language standardized in the United States. Since that intital achievement, study and application of the standard specifications have revealed the need for maintenance of the standards. As the result of work intiated in 1967, as initial set of clarifying interpretations has been prepared. The nature of the maintenance, corrections to the standard specifications, and completed interpretations are reported.
Research and Advances

An automatic grading scheme for simple programming exercises

A discussion is given of alterations that were made to a typical university operating system to record the results of programming exercises in three different languages, includeing assembly language. In this computer-controlled grading scheme provision is made for testing with programmer-supplied data and for final runs with system-supplied data. Exercises run under the scheme may be mixed with other programs, and no special recognition of exercises by the operators is necessary.
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Research and Advances

Analysis of boolean program models for time-shared, paged environments

Directed graphs or their associated matrices are frequently used to represent the logical structure of sequences of computer instructions. Such techniques are used and, in addition, data references are represented in a nondirected model. The complete structural specification of a program is represented by a combined model. A transformation of the combined model yields a new model in which additional timing information is also contained. Analysis of these models prior to execution yields information valuable in determining segmentation of instructions and data for a time-shared environment, as well as for initial page loading; during execution, the analysis may be used for “look ahead” control of page turning.
Research and Advances

Organizing matrices and matrix operations for paged memory systems

Matrix representations and operations are examined for the purpose of minimizing the page faulting occurring in a paged memory system. It is shown that carefully designed matrix algorithms can lead to enormous savings in the number of page faults occurring when only a small part of the total matrix can be in main memory at one time. Examination of addition, multiplication, and inversion algorithms shows that a partitioned matrix representation (i.e. one submatrix or partition per page) in most cases induced fewer page faults than a row-by-row representation. The number of page-pulls required by these matrix manipulation algorithms is also studied as a function of the number of pages of main memory available to the algorithm.
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Research and Advances

Data communications control procedures for the USA standard code for information interchange

This proposed American Standard has been accepted for publication by USA Standards Committee X3, Computers and Information Processing. In order that the final version of the proposed standard reflect the largest public consensus, X3 authorized publication of this document to elicit comment and general public reaction, with the understanding that such a working document is an intermediate result in the standardization process and is subject to change, modification, or withdrawal in part or in whole. Comments should be addressed to the X3 Secretary, Business Equipment Manufacturers Association, 235 East 42 Street, New York, NY 10017.—E. L.
Research and Advances

Extremely portable random number generator

Extremely portable subroutines are sometimes needed for which moderate quality and efficiency suffice. Typically, this occurs for library functions (like random number generation and incore sorting) which are not entirely universal or are not used in a standardized way. The literature on random number generators does not seem to contain an algorithm that meets requirements of this sort. An extremely portable 8-line FORTRAN program is provided which is based on an important paper by Coveyou and MacPherson (1967). Using their methods, Fourier analysis is applied to the probability function for the consecutive n-tuples provided by our generator (with n less than or equal to 4). While the small modulus which must be used to maintain portability prevents the quality of the generator from being high, the generator compares well with the bounds established in the above mentioned paper.
Research and Advances

Exclusive simulation of activity in digital networks

A technique for simulating the detailed logic networks of large and active digital systems is described. Essential objectives sought are improved ease and economy in model generation, economy in execution time and space, and a facility for handling simultaneous activities. The main results obtained are a clear and useful separation of structural and behavioral model description, a reduction of manual tasks in converting Boolean logic into a structural model, the elimination of manual processes in achieving exclusive simulation of activity, an event-scheduling technique which does not deteriorate in economy as the event queue grows in length, and a simulation procedure which deals effectively with any mixture of serial and simultaneous activities. The passage of time is simulated in a precise, quantitative fashion, and systems to be simulated may be combinations of synchronous and asynchronous logic. Certain aspects of the techniques described may be used for the simulation of network structures other than digital networks.
Research and Advances

Some criteria for time-sharing system performance

Time-sharing systems, as defined in this article, are those multiaccess systems which permit a terminal user to utilize essentially the full resources of the system while sharing its time with other terminal users. It is each terminal user's ability to utilize the full resources of the system that makes quantitative evaluation of time-sharing systems particularly difficult. Six criteria are described which have been successfully used to perform first-level quantitative time-sharing system performance evaluation.
Research and Advances

Directed random generation of sentences

The problem of producing sentences of a transformational grammar by using a random generator to create phrase structure trees for input to the lexical insertion and transformational phases is discussed. A purely random generator will produce base trees which will be blocked by the transformations, and which are frequently too long to be of practical interest. A solution is offered in the form of a computer program which allows the user to constrain and direct the generation by the simple but powerful device of restricted subtrees. The program is a directed random generator which accepts as input a subtree with restrictions and produces around it a tree which satisfies the restrictions and is ready for the next phase of the grammar. The underlying linguistic model is that of Noam Chomsky, as presented in Aspects of the Theory of Syntax. The program is written in FORTRAN IV for the IBM 360/67 and is part of a unified computer system for transformational grammar. It is currently being used with several partial grammars of English.
Research and Advances

Object code optimization

Methods of analyzing the control flow and data flow of programs during compilation are applied to transforming the program to improve object time efficiency. Dominance relationships, indicating which statements are necessarily executed before others, are used to do global common expression elimination and loop identification. Implementation of these and other optimizations in OS/360 FORTRAN H are described.
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Research and Advances

The role of programming in a Ph.D. computer science program

In this general paper the role of programming in advanced graduate training is discussed. Subject matter related to programming as well as programming per se is considered. The importance and application of formalism are considered and also the need for good empirical experimentation. A brief outline for a sequence of courses is included, and subject headings that have been obtained from an extensive bibliography are given. A bibliography of programming references is included.
Research and Advances

A system organization for resource allocation

This paper introduces a system for resource management using the concepts of “process,” “facility,” and “event.” Except for the processor no attempt has been made to give serious suggestions for the policy to be followed for resource allocation. However, a basic framework is provided in which a system analyst can express solutions to resource management problems. The paper is divided into a tutorial presentation, a description of the system primitives, and a small collection of examples of the use of the primitives.
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Research and Advances

A SIMSCRIPT-FORTRAN case study

Two programs for a vehicle dispatching model, one written in 7040 SIMSCRIPT and the other in 7040 FORTRAN IV are compared. The comparison is made in terms of basic program design decisions, storage requirements, computer time used, and the ease of making changes. In the SIMSCRIPT program, the primary design considerations center around the choice of model variables, model changing events, and model testing. In the FORTRAN program, basic design problems relate to the representation of the passage of time, the allocation of storage, and the organization of input data. The comparison of these differently designed programs shows that the SIMSCRIPT program uses more computer storage and more computer time, but requires fewer program changes to introduce model revisions.
Research and Advances

GEORGE 3—A general purpose time sharing and operating system

An Operating System is described which will run on a wide variety of configurations of the I.C.T. 1900, and can handle a large number of online console users while at the same time running several offline (background) jobs. The system is not oriented towards either mode and can be either a batch processing system (such as the ATLAS Supervisor, IBSYS, or GECOS), or a multiaccess system (resembling, to the user, CTSS or MULTICS), or both simultaneously, depending on the installation, which can adjust the Schedulers. Both online users and offline jobs use a common Command Language. The system includes a Multilevel device-independent File Store.
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Research and Advances

An experimental model of system/360

The problem of predicting the performance of modern computer systems is formidable. One general technique which can ease this problem is macroscopic simulation. This paper reports on the applicability of that technique to System/360. The paper describes an experimental model of System/360—its hardware, software, and its environment. The measures of system performance produced by the model consist of statistics relating to turnaround time, throughput, hardware utilization, software utilization, and queueing processes. The model is mechanized in SIMSCRIPT and consists of some 1750 statements. An auxiliary program, the Job Generator, creates automatically the properties of System/360 jobs that get simulated.
Research and Advances

Automatic data compression

The “information explosion” noted in recent years makes it essential that storage requirements for all information be kept to a minimum. A fully automatic and rapid three-part compressor which can be used with “any” body of information to greatly reduce slow external storage requirements and to increase the rate of information transmission through a computer is described in this paper. The system will also automatically decode the compressed information on an item-by-item basis when it is required. The three component compressors, which can be used separately to accomplish their specific tasks, are discussed: NUPAK for the automatic compression of numerical data, ANPAK for the automatic compression of “any” information, and IOPAK for further compression of information to be stored on tape or cards.
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