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.
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