US5715455A
Expired / Lapsed
US
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Apparatus and method for storing file allocation table efficiently in memory
Assignee: International Business Machines Corp
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Filing: 1995-05-18
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Granted: 1998-02-03
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Expires: 2015-05-18
Abstract
Abstract A data processing system, such as a personal computer, contains a file allocation table that is stored in memory in a packed format. During initialization, file allocation tables stored on an external storage device are "packed" and stored in a region of memory and subsequently "unpacked" during a read operation.
Inventors
- 👤 James Franklin Macon, Jr.
- 👤 David Medina
- 👤 Mark Alan Peloquin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 22:41
CPC Classifications
G; G06; G06F; G06F16/00; G06F16/10; G06F16/90; G06F16/901; G06F16/9017; Y; Y10; Y10S; Y10S707/00; Y10S707/99931; Y10S707/99932; Y10S707/99951; Y10S707/99956
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
191 words
In a personal computer system comprising an operating system, random access memory (RAM) and a file allocation table (FAT) normally stored in definable FAT storage units on an external storage device, wherein the file allocation table represents a mapping of data stored on the external storage device having a plurality of tracks, each track having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the improvement comprising: means for storing said file allocation table in a packed format in the RAM of the personal computer such that, during an I/O operation, the external storage device need not be accessed to retrieve entries from the file allocation table; means for grouping a first contiguous range of clusters into a first group of clusters; means for allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and means for setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
Claim 2
Dependent Claim
191 words
In a personal computer system comprising an operating system, random access memory (RAM) and a file allocation table (FAT) normally stored in definable FAT storage units on an external storage device, wherein the file allocation table represents a mapping of data stored on the external storage device having a plurality of tracks, each track having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the improvement comprising: means for storing said file allocation table in a packed format in the RAM of the personal computer such that, during an I/O operation, the external storage device need not be accessed to retrieve entries from the file allocation table; means for grouping a first contiguous range of clusters into a first group of clusters; means for allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and means for setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
Claim 3
Dependent Claim
22 words
The improvement of claim 1 further comprising: means for linking said first contiguous group of clusters to a subsequent group of cluster.
Claim 4
Dependent Claim
40 words
The improvement of claim 1 further comprising: means for assigning a pseudo cluster value for certain ones of said clusters wherein said pseudo cluster value represents a logical address within a contiguous range of clusters on said external storage device.
Claim 5
Dependent Claim
239 words
In a personal computer system comprising an operating system, random access memory (RAM) and a file allocation table (FAT) normally stored in definable FAT storage units on an external storage device, wherein the file allocation table represents a mapping of data stored on the external storage device having a plurality of tracks, each track having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the improvement comprising: means for storing said file allocation table in a packed format in the RAM of the personal computer such that, during an I/O operation, the external storage device need not be accessed to retrieve entries from the file allocation table; means for assigning a pseudo cluster value for certain ones of said clusters wherein said pseudo cluster value represents a logical address within a contiguous range of clusters on said external storage device; means for grouping a first contiguous range of clusters into a first group of clusters; means for linking said first contiguous group of clusters to a subsequent group of clusters; means for allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and means for setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
Claim 6
Dependent Claim
239 words
In a personal computer system comprising an operating system, random access memory (RAM) and a file allocation table (FAT) normally stored in definable FAT storage units on an external storage device, wherein the file allocation table represents a mapping of data stored on the external storage device having a plurality of tracks, each track having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the improvement comprising: means for storing said file allocation table in a packed format in the RAM of the personal computer such that, during an I/O operation, the external storage device need not be accessed to retrieve entries from the file allocation table; means for assigning a pseudo cluster value for certain ones of said clusters wherein said pseudo cluster value represents a logical address within a contiguous range of clusters on said external storage device; means for grouping a first contiguous range of clusters into a first group of clusters; means for linking said first contiguous group of clusters to a subsequent group of clusters; means for allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and means for setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
Claim 7
Independent Claim
136 words
A method in a computer system for storing a file allocation table (FAT) in a packed format in a random access memory of the computer system, wherein the file allocation table represents a mapping of data stored on an external storage device having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the method comprising the steps of: grouping a first contiguous range of clusters into a first group of clusters; allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
Claim 8
Independent Claim
136 words
A method in a computer system for storing a file allocation table (FAT) in a packed format in a random access memory of the computer system, wherein the file allocation table represents a mapping of data stored on an external storage device having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the method comprising the steps of: grouping a first contiguous range of clusters into a first group of clusters; allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
Claim 9
Dependent Claim
23 words
The method of claim 5 further comprising the step of: linking said first contiguous group of clusters to a subsequent group of clusters.
Claim 10
Dependent Claim
41 words
The method of claim 5 further comprising the step of: assigning a pseudo cluster value for certain ones of said clusters wherein said pseudo cluster value represents a logical address within a contiguous range of clusters on said external storage device.
Claim 11
Independent Claim
181 words
A method in a computer system for unpacking a file allocation table (FAT) stored in a packed format in a random access memory of the computer system, wherein the file allocation table represents a mapping of data stored on an external storage device having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the method comprising the steps of: assigning a pseudo cluster value for certain ones of said clusters wherein said pseudo cluster value represents a logical address within a contiguous range of clusters on said external storage device; grouping a first contiguous range of clusters into a first group of clusters; linking said first contiguous group of clusters to a subsequent group of clusters; allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
Claim 12
Independent Claim
181 words
A method in a computer system for unpacking a file allocation table (FAT) stored in a packed format in a random access memory of the computer system, wherein the file allocation table represents a mapping of data stored on an external storage device having a plurality of sectors, each sector having a plurality of storage locations, wherein one or more sectors may be represented by a single cluster, the method comprising the steps of: assigning a pseudo cluster value for certain ones of said clusters wherein said pseudo cluster value represents a logical address within a contiguous range of clusters on said external storage device; grouping a first contiguous range of clusters into a first group of clusters; linking said first contiguous group of clusters to a subsequent group of clusters; allocating a bitmap for a given FAT storage unit, said bitmap having a bit for each cluster address within said given FAT storage unit; and setting a bit in said bitmap, to indicate that certain ones of said cluster addresses within said given FAT storage unit represent an end-of-file cluster.
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