Software Engineering and Programming Languages
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President’s letter to the ACM membership
Computer programming deals with an enormous variety of activities and is carried on by people with a great variety of backgrounds. It seems clear that part but not all of this activity is evolving toward a distinct professional field, but that the scope of this emerging profession, and some of its economic, social, and educational characteristics are as yet by no means well defined. In this paper, these issues are examined and some opinions about them are expressed.
Structure of a LISP system using two-level storage
In an ideal list-processing system there would be enough core memory to contain all the data and programs. Described in this paper are a number of techniques that have been used to build a LISP system utilizing a drum for its principal storage medium, with a surprisingly low time penalty for use of this slow storage device. The techniques include careful segmentation of system programs, allocation of virtual memory to allow address arithmetic for type determination, and a special algorithm for building reasonably linearized lists. A scheme for binding variables is described which is good in this environment and allows for complete compatibility between compiled and interpreted programs with no special declarations.
Application of level changing to a multilevel storage organization
A technique for organizing the devices of a computer storage system is described. This technique, called the multilevel store, provides a means for economically satisfying the requirements for very large storage capacities of certain data management and information retrieval systems. The concept of level changing is introduced and its application to the multilevel store is discussed. A possible means for physically organizing the information for efficient use of the multilevel store is presented.
Computer programming deals with an enormous variety of activities and is carried on by people with a great variety of backgrounds. It seems clear that part but not all of this activity is evolving toward a distinct professional field, but that the scope of this emerging profession, and some of its economic, social, and educational characteristics are as yet by no means well defined. In this paper, these issues are examined and some opinions about them are expressed.
On the automatic simplification of source-language programs
Methods of simplification that can be applied automatically to programs written in an ALGOL-like language are discussed. The simplifications are based on the form of the program and the knowledge obtained by a processor, without any understanding of what the program is supposed to do. These methods have been implemented in a processor called SURE that accepts a program written in JOVIAL and outputs an equivalent JOVIAL program that may be shorter and may be executed faster than the original.
SURE is described, some of the problems encountered in automatic improvement at the source-language level are discussed, and further types of automatic program improvement are suggested.
The Nebulous future of machine translation
A report by the National Academy of Sciences that examines machine translation against the light of human translation has disturbed a good many research administrators in the government. So much bad publicity has been engendered by this report that the future of machine translation is uncertain, even though the technology is a scant twelve years old.
Examples of algorithms that will accomplish automatic storage reservation without the need for explicit array declarations are described.
During the past year, the Communications has printed approximately twenty papers in each of three main areas: programming language development, compiler management and construction, and numerical methods. In addition, about twenty new algorithms were published, as well as half a dozen papers covering the general area of education in computer science; new proposed standards were also disseminated for various types of paper tape, punched cards, and for data communication codes. Three of the twelve issues were conference issues consisting of papers originally given at the ACM Conference on Programming Languages and Pragmatics, the ACM Symposium on Symbolic and Algebraic Manipulation, and a Symposium on the Impact of Computing on Undergraduate Mathematics. A survey paper was published on simulation languages, and two reports were printed covering the computer scene in Communist China and Europe, respectively.
DITRAN—a compiler emphasizing diagnostics
DITRAN DIagnostic FORTRAN) is an implementation of ASA Basic FORTRAN with rather extensive error checking capabilities both at compilation time and during execution of a program. The need for improved diagnostic capabilities and some objectives to be met by any compiler are discussed. Attention is given to the design and implementation of DITRAN and the particular techniques employed to provide the diagnostic features. The handling of error messages by a general macro approach is described. Special features which provide teaching aids for use by instructors are noted.
System performance evaluation: survey and appraisal
The state of the art of system performance evaluation is reviewed and evaluation goals and problems are examined. Throughput, turnaround, and availability are defined as fundamental measures of performance; overhead and CPU speed are placed in perspective. The appropriateness of instruction mixes, kernels, simulators, and other tools is discussed, as well as pitfalls which may be encountered when using them. Analysis, simulation, and synthesis are presented as three levels of approach to evaluation, requiring successively greater amounts of information. The central role of measurement in performance evaluation and in the development of evaluation methods is explored.
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