Search

Presents several letters to the editor. Focus on the trial of executive Robert Tappan Morris for bringing the Internet research computer network to a standstill; Comment on the article "Results of the Nineteenth ACM North American Computer Chess Championship," published in the October 1989 issue of the journal "Communications"; Information on the article "Computerization, Productivity, and Quality of Work-Life," published in the February 1989 issue of the journal "Communications."

In this paper we describe a practical method of partial-match retrieval in very large data files. A binary code word, called a descriptor, is associated with each record of the file. These record descriptors are then used to form a derived descriptor for a block of several records, which will serve as an index for the block as a whole; hence, the name "indexed descriptor files." First the structure of these files is described and a simple, efficient retrieval algorithm is presented. Then its expected behavior, in terms of storage accesses, is analyzed in detail. Two different tile creation procedures are sketched, and a number of ways in which the file organization can be "tuned" to a particular application are suggested. [ABSTRACT FROM AUTHOR]

A scheme is described which permitting a substantial increase in memory space utilized to store list-structured data. It consists in reducing to one level a nonhomogeneous store composed of fast (core) and slow (disk or drum) memories. The space available in slow memory is divided into pages each containing a given number of machine words. The reduction to a one-level memory is performed by a program which leaves the most often called pages in the fast memory. When a new page from slow store is requested, the page in core having the longest period of inactivity is transferred back to the slow store. The complete scheme has been implemented in connection with a LISP embedding into ALGOL using an IBM 7044 with 32K of core memory and disks. Gains in memory space were about 100-fold. As often happens in programming applications the price of the additional space is computer time. Although the disks have an access time 104 limes slower than core, tests indicate that the actual slow down varied from 3 to 10, depending on the number of pages available in the fast store. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]