Browse Prior Art Database

STORAGE STRUCTURE AND MANAGEMENT IN THE SNOBAT IMPLEMENTATION OF SNOBOL4

IP.com Disclosure Number: IPCOM000127994D
Original Publication Date: 1976-Dec-31
Included in the Prior Art Database: 2005-Sep-14
Document File: 11 page(s) / 42K

Publishing Venue

Software Patent Institute

Related People

Stefan M. Silverston: AUTHOR [+3]

Abstract

The purpose of the paper is to present the SNOBAT storage system, and to discuss the considerations and trade-offs behind it. The over-all scheme, with its provision for adjustment to meet the needs of particular programs, is covered first,'.'fhen the scheme used for data storage and retrieval and for memory re-clamation is described. The storage management of SNOBOL4 patterns is examined. Finally, the PURGE primitive, a unique feature of SNOBAT, is presented. Details of storage structure, as exemplified in the figures used for illus-tration, reflect IBM 360 architecture 9. Words consist of 4 8-bit bytes. Addresses require 3 bytes, and are typically stored in.the low-order three bytes of words.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 9% of the total text.

Page 1 of 11

THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

STORAGE STRUCTURE AND MANAGEMENT IN THE SNOBAT IMPLEMENTATION OF SNOBOL4

by Stefan M. Silverston Technical Report #76-14 December 1976

Storage Structure and Management in the SNOBAT Implementation of SNOBOL4

Stefan M. Silverston Department of Computer Scienoe Iowa State University Ames, Iowa 50011 USA November 12, The purpose of the paper is to present the SNOBAT storage system, and to discuss the considerations and trade-offs behind it. The over-all scheme, with its provision for adjustment to meet the needs of particular programs, is covered first,'.'fhen the scheme used for data storage and retrieval and for memory re-clamation is described. The storage management of $NOBOL4 patterns is examined. Finally, the PURGE primitive, a unique feature of SNOBAT, is presented. Details of storage structure, as exemplified in the figures used for illus-tration, reflect IBM 360 architecture 9. Words consist of 4 8-bit bytes. Addresses require 3 bytes, and are typically stored in.the low-order three bytes of words,

OVER-ALL STORAGE CAB

SNOBOL4 information falls into several categories. For example, there are descriptors of data objects, data objects themselves, and dope vectors for de-fined data structures. Memory overflow for a particular program is often the re-sult of excessive memory requirement for information of just one category, The SNOBAT implementation attempts to provide some flexibility. Memory is organized in 'j regions, each essentially associated with information of a particular cat-

egory. The size of each region can be set separately by the programmers extern-

'' ~t ally to the SNOBOL4 program. SNOBAT memory organization is depicted in Figure 1. Note that space is economized by allowing upward and downward expansion into the same free areas: STACK and RESERVE regions; indexed and non-indexed parts of NAME region; tempo- rary and permanent parts of VALUE region,

The STACK region holds the run-time stack used for function linkage, Since Sizes are transmitted via PARM field of EXEC card in OS JCL. See manual for SNOBAT 1.98, page 24 et seq,

(Image Omitted: Figure 1. SNOUT memory organization.)

all SNOBOL4 function calls are potentially recursive, a stack entry must be made every time a function is called. Stack entries consist mainly of descriptors of variables which must be preserved prior to transfer of control to the function. Programs which involve much use of nested function recursion, especially if parameter and local-variable lists are long, :require large STACK regions. '1 'he STACK region is also used for an auxiliary stack during pattern matching, The RESERVE region is used for non-reclaimable storage. This includes

1, data control blocks for peripheral I/0 2, run-time compiled code

Iowa State University Page 1 Dec 31, 1976

Page 2 of 11

STORAGE STRUCTURE AND MANAGEMENT IN THE SNOBAT IMPLEMENTATION OF SNOBOL4

3, data-structure descriptors

4. long patterns...