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THE UNIVERSITY OF MICHIGAN Memorandum 25 MODIFICATIONS TO THE SEL EXECUTIVE SYSTEM

IP.com Disclosure Number: IPCOM000128388D
Original Publication Date: 1970-Feb-01
Included in the Prior Art Database: 2005-Sep-15
Document File: 4 page(s) / 19K

Publishing Venue

Software Patent Institute

Related People

Jackson, James H.: AUTHOR [+4]

Abstract

Some modifications to the SEL Executive System are described which improve the performance of the system, but which do not change the set of system subroutines, the entry point to any system subroutine, or the calling sequence for any system subroutine. User programs which run with the original version of the system need not be changed in order to run with the new version of the system.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 35% of the total text.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

THE UNIVERSITY OF MICHIGAN Memorandum 25 MODIFICATIONS TO THE SEL EXECUTIVE SYSTEM

James H. Jackson James F. Blinn

CONCOMP: Research in Conversational Use of Computers ORA Project 07449
F. H. Westervelt, Director

supported by DEPARTMENT OF DEFENSE ADVANCED RESEARCH PROJECTS AGENCY WASHINGTON, D. C.

CONTRACT NO. DA-49-083 OSA-3050 ARPA ORDER NO. 716

administered through: OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR February 1970

ABSTRACT

Some modifications to the SEL Executive System are described which improve the performance of the system, but which do not change the set of system subroutines, the entry point to any system subroutine, or the calling sequence for any system subroutine. User programs which run with the original version of the system need not be changed in order to run with the new version of the system.

TABLE OF CONTENTS

ABSTRACT.....iii
1. Introduction.....1
2. Alphanumeric Tape Format.....2
3. Response to Empty Task Queue.....4
4. Display Structure Modification.....

[ Chapter ] 1. INTRODUCTION

University of Michigan Page 1 Feb 01, 1970

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THE UNIVERSITY OF MICHIGAN Memorandum 25 MODIFICATIONS TO THE SEL EXECUTIVE SYSTEM

This paper describes several modifications which have been made to the SEL Executive System since it was documented1. These modifications were intended to improve the performance of the system, rather than to extend the set of operations which it performs. Consequently, neither the vector of system subroutine entry points nor the calling sequence to any system subroutine has been changed. User programs which run with the original version of the system (Version 1) need not be changed in order to run with the new version of the system (Version 2).

[ Chapter ] 2. ALPHANUMERIC TAPE FORMAT

Each 8-bit alphanumeric tape image for use with the system originally consisted of two control bits (l12 followed by a 6-bit character code [ 1 pp. 23-24 ] . An alphanumeric record was a sequence of these tape images, followed by an end- of-record character (0008. This format was adopted because, through examination of the control bits, a program (e.g., a copy function in the idle-time task) could easily determine whether it was reading an alphanumeric record or a binary record. In this way, the system was protected against the user's inadvertent attempt to load an alphanumeric record. With this protection provided, interspersing descriptive text with binary records was practical.

Since the ability to list alphanumeric tapes on an off-line teletype is desirable, the alphanumeric tape format has been changed from the 6-bit code format to an ASCII code format. The only changes to the system which were required by this change of format were in the copy functions of the idle-time task which involve reading or punching of alphanumeric tape. Each record in the new alphanumeric tape format consists of a sequence of ASCII characters with the parity bit p...