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Ambiguity Minimizing Algorithm for Op Code Description Tables

IP.com Disclosure Number: IPCOM000091218D
Original Publication Date: 1969-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Atkins, JD: AUTHOR

Abstract

In free-form coding, a significant problem is that of identifying instruction types with a minimum of effort. This is accomplished by using a table of op-code descriptions. Each table element contains the ordered unique parts of an op-code. Before such a table is used for instruction identification, the ambiguity within the table must be resolved by rearrangement of the table. Thus, any op-code description which has all of another op-code as its leading parts and contains additional trailing parts is placed in the table for use in identification of an op-code before the other is used. This algorithm achieves this result. PL/1 functions INDEX and SUBSTR are utilized in a twenty-eight instructions routine.

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Ambiguity Minimizing Algorithm for Op Code Description Tables

In free-form coding, a significant problem is that of identifying instruction types with a minimum of effort. This is accomplished by using a table of op-code descriptions. Each table element contains the ordered unique parts of an op- code. Before such a table is used for instruction identification, the ambiguity within the table must be resolved by rearrangement of the table. Thus, any op- code description which has all of another op-code as its leading parts and contains additional trailing parts is placed in the table for use in identification of an op-code before the other is used. This algorithm achieves this result. PL/1 functions INDEX and SUBSTR are utilized in a twenty-eight instructions routine. At the termination of the routine, the table of op-code descriptions is suitable for unambiguous use in identifying instruction types.

The op-code parts within each table entry are delimited by a nonprintable EBCDIC character, i.e., an 8-9 punch. As indicated in the flow chart, the algorithm consists of a double DO loop. The outer parameter I ranges from one to N-1, where the op-code description table contains N elements. The inner parameter J ranges from I+1 to N. An attempt is made to identify each element J using the op-code description in element I. If an attempt is successful, element J is moved to the Ith position and elements I through J-1 are pushed down one position. The search routine conti...