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Automatic Definition of Tables by an Assembly Loop

IP.com Disclosure Number: IPCOM000074163D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Couland, G: AUTHOR

Abstract

A program written in assembly language uses several tables which are modular in size, and the contents of which are governed by iterative rules. Such tables are generally written by using a macrolanguage, which leads to write heavy coding of nested expanded loops. Automatic definition of these tables can be achieved by using an assembly language facility which permits duplication of a specified set of instructions a specified number of times, with possible changes in the set each time it is duplicated. The changes and the count of iterations are deduced from a set of values successively assigned to a symbolic parameter. The set of values can be defined either by a recurrent method or by a descriptive list. 1. Syntax.

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Automatic Definition of Tables by an Assembly Loop

A program written in assembly language uses several tables which are modular in size, and the contents of which are governed by iterative rules. Such tables are generally written by using a macrolanguage, which leads to write heavy coding of nested expanded loops. Automatic definition of these tables can be achieved by using an assembly language facility which permits duplication of a specified set of instructions a specified number of times, with possible changes in the set each time it is duplicated. The changes and the count of iterations are deduced from a set of values successively assigned to a symbolic parameter. The set of values can be defined either by a recurrent method or by a descriptive list. 1. Syntax.

The set of instructions to be duplicated is called an ALOOP (Assembly Loop) block; it must be preceded by an ALOOP header instruction and followed by an ALOOP trailer instruction, with the following format: Operation Operand ALOOP Control field, Loop Parameters Header ALOOP Blank Trailer Control has either of the formats: Control symbol Control symbol (Pattern). where control symbol denotes a $ character followed by one letter, and Pattern denotes an absolute expression. If Pattern is absent, the hexadecimal value FFFF is assumed. Loop parameters have either of the following formats: First, Last, Step, Until =(E1,E2
......, EK)Until.

First, Last, Step, Until denotes absolute expressions. Until and its preceding comma may be omitted, in which case the value 4095 is assumed. If Until is omitted, Step and its preceding comma may be omitted, in which case the value 1 is assumed. E1, E2, Ek, denote a set of absolute expressions or a set of alphanumeric constants. Any instruction, including the instruction ALOOP, may appear in an ALOOP block. This allows nesting of ALOOP blocks. The Control symbol may be used in any field of an instruction but must not appear as the Control symbol in an inner ALOOP header. 2. Control Symbol values.

The assembler uses the Loop parameters to determine a set of n edited values V1...