Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-01-08
2001-04-10
Nguyen, Hiep T. (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S173000, C707S793000, C235S380000, C235S492000
Reexamination Certificate
active
06216204
ABSTRACT:
The present invention relates to an integrated circuit (IC) card including a memory containing files classified in a tree structure.
BACKGROUND OF THE INVENTION
For reasons associated with communications protocol and convenience of use, the files in an IC card memory are classified in directories, themselves organized in a tree structure having various levels. A given file thus corresponds to a particular access path in the tree structure.
At present, the tree structure is implemented physically in the card memory: the directories in which the various files are stored are physically created in the memory and they are physically interleaved amongst one another in application of a tree structure created by the user.
That method of storing files with a physical tree structure suffers from two main drawbacks. Firstly it is expensive in memory space, since the directories of the tree structure exist physically within the memory and the header information they contain (identifiers, sizes, pointers, etc. . . . ) occupies memory space that cannot be used for storing files. Secondly, the operations of adding, deleting, extending, or reducing a file require physical modification to the tree structure in the memory. Such modification assumes that the chaining pointers of the tree structure are updated dynamically. This updating gives rise not only to a loss of time, but also to insecurity, in the event of the card being pulled out while updating is taking place, in which case there is a risk that the operating system will no longer be able to reestablish a coherent tree structure in the card memory.
OBJECT AND SUMMARY OF THE INVENTION
According to the invention, an IC card is proposed including a memory containing files classified in a tree structure having various levels, each file having an associated access path, in which each file is physically located in the memory independently of its location in the virtual tree structure, and contains information specifying the full access path associated with the file.
Thus, the card memory no longer has a physical tree structure. Nevertheless, the access path contained in each file makes it possible, a posteriori, to reconstitute the tree structure in which the various files are classified for the needs of communications protocol or for convenience of use.
The absence of a physical tree structure facilitates and makes secure the operations of adding, deleting, extending, or reducing files. For example, a file is added merely by writing the file in memory after files that already exist, or in any available memory block. Similarly, deleting a file does not necessarily require existing files to be moved. If the card is pulled out while such operations are taking place, the access path of each file is not damaged in any way, and the operating system will be capable of accessing the various files in the future without any particular difficulty, with only the file that was in the process of being modified at the time the card was pulled out running any risk of being affected.
Advantageously, each file contains information specifying the level of its location in the tree structure. Thus, when the operating system is looking for a file at a given level, it is possible for it to examine the access paths only of those files at the same level as the looked-for file. File searching is thus accelerated.
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patent: 5600821 (1997-02-01), Falik et al.
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Frenger P: “MCard/FS: afile manager for memory cards” Images of the Twenty-First Century. Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Cat. No. 89CH2770-6), Seattle, WA, USA, Nov. 9-12, 1989, 1989, New York NY, USA, IEEE, pp. 777-778 vol. 2, XP002029716.
Birch & Stewart Kolasch & Birch, LLP
Nguyen Hiep T.
Schlumberger Systemes
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