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Instruction Constant Distinguishability

IP.com Disclosure Number: IPCOM000090328D
Original Publication Date: 1969-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Miller, IM: AUTHOR

Abstract

The drawing shows part of disassembler which operates on a program in machine language to produce a sequence of constants and instructions in a higher level language. Disassemblers are useful for understanding machine language programs and for translating programs from one machine language to another by first disassembling the program.

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Instruction Constant Distinguishability

The drawing shows part of disassembler which operates on a program in machine language to produce a sequence of constants and instructions in a higher level language. Disassemblers are useful for understanding machine language programs and for translating programs from one machine language to another by first disassembling the program.

All instructions contain distinctive op codes. Constants can have any form. A constant can have a form that identifies it as not an instruction but it also can resemble an instruction. As drawing part A shows, a piece of code is tentatively classified as a constant or an instruction according to whether it contains a possible op code. Branch instructions are separately identified by their op codes and are used in the sequence of drawing part B. Other instructions are identified and added to a list of the instructions of the current sequence. A word that does not contain a possible op code is classified as a constant.

Drawing parts B and C show operations to check the tentative classification of a piece of code as an instruction. Valid instruction sequences end with a branch instruction. Branch instructions also occur within sequences of constants, but such a branch instruction is referenced by an execute instruction. In drawing part B, a tentatively identified branch instruction that is referenced as a constant is reclassified as a constant and is handled according to drawing part A. A branch...