Abstract:
A memory device, system and method of editing a file in a non-volatile memory device is described. The memory device includes a controller and a memory array configured to copy an existing first file into a second file during editing and to maintain the first file while applying edits to the second file. When editing is completed, a first cluster pointer of the first file is redirected to point at the first cluster of the second file that has been edited.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/182,845, filed Feb. 18, 2014, pending, which continuation of U.S. patent application Ser. No. 13/043,968, filed Mar. 9, 2011, now U.S. Pat. No. 8,655,927, issued Feb. 18, 2014, which is a continuation of U.S. patent application Ser. No. 11/725,879, filed Mar. 20, 2007, now U.S. Pat. No. 7,917,479, issued Mar. 29, 2011, the disclosure of each of which is hereby incorporated herein in its entirety by this reference. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments of the present invention relate generally to the field of non-volatile memory devices and, more particularly, to protecting file integrity of data stored on a non-volatile memory device. 
       BACKGROUND 
       [0003]    Electronic or computer systems employ multiple memory types, which may be grouped according to volatile and non-volatile capabilities. Non-volatile memory types retain stored data even when no electrical power is being supplied to the electronic system. Electronic systems may include various types of non-volatile memory devices such as disk drives including magnetic drives commonly referred to as “hard drives.” Disk drive systems typically excel in the ability to store and retrieve large quantities of data. Hard drive form factors have evolved to include portable removable media such as memory cards, memory sticks, Flash cards and Flash drives. Due to their portable nature, these types of memories include electromechanical interface components that may be timely or untimely disconnected from their host system or otherwise have their power source untimely interrupted. Furthermore, these removable non-volatile memory devices often incorporate data retention technology that is sluggish in writing or programming data to the storage medium. Accordingly, the probability that a power interruption may occur when data is being written to the memory device is significant enough to require attention. 
         [0004]    A file allocation table (FAT) is associated with the storage media in order to be able to determine which data was written to the medium, and to be able to determine a place on the medium where the stored data is located. Several different kinds of FAT standards have been developed, including FAT12, FAT16 and FAT32, to address needs of different systems. In a conventional FAT file system, new data or changes to an existing file are written over and/or appended to a previous version of the file when a file is modified. Following writing of the new data or changes, the FAT is updated providing the memory device remains attached and powered. However, a conventional FAT file system is vulnerable to corruption from an interrupted write or programming operation of the memory device resulting from, for example, an intervening power loss such as when the memory device or the power source to the memory device is prematurely disconnected. 
         [0005]    Should a power interruption occur after initiation of a write of new data to a file, but before or during the corresponding FAT write operation, the entire file system can be damaged or destroyed. While the likelihood of a complete file system loss is small, there is a large probability of lost data segments configured as cluster chains that may or may not be recoverable following restoration of power to the device. Conventional FAT file systems, by design, are not transaction-safe file systems. The conventional FAT can be corrupted when a write or programming operation is interrupted during a file editing process resulting in corruption of a file or entire loss of some data within the file. 
         [0006]    For the reasons stated above, and for other reasons stated below which will become apparent to those of ordinary skill in the art upon reading and understanding the present specification, there is a need in the art for improved non-volatile memory devices. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]      FIG. 1  is a simplified diagram of an embodiment of a system that incorporates a non-volatile memory device, in accordance with embodiments of the present invention. 
           [0008]      FIGS. 2A and 2B  illustrate encoding of user data into blocks and sectors in a non-volatile memory array, in accordance with various embodiments of the present invention. 
           [0009]      FIG. 3  is a memory map of a non-volatile memory array partitioned according to a file system, in accordance with various embodiments of the present invention. 
           [0010]      FIG. 4  illustrates storage of an existing file stored in a file system. 
           [0011]      FIG. 5  illustrates editing of an existing file in a file system. 
           [0012]      FIGS. 6A-6D  illustrate editing of an existing file in a file system, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    In the following detailed description, reference is made to the accompanying drawings that form a part hereof and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized, and that structural, logical and electrical changes may be made without departing from the spirit and scope of the present invention. 
         [0014]    Many computer operating systems, such as “DOS” (Disk Operating System), support the physical characteristics of hard drive structures and support file structures based on heads, cylinders and sectors. By way of example and not limitation, a DOS software-based system stores and retrieves data based on these physical attributes. Magnetic hard disk drives operate by storing polarities on magnetic material. This material is able to be rewritten quickly and as often as desired. These characteristics allow DOS to develop a file structure that stores files at a given location, which is updated by a rewrite of that location as information is changed. Essentially all locations in DOS may be viewed as fixed and do not change over the life of the disk drive being used therewith, and are easily updated by rewrites of the smallest supported block of this structure. A sector (of a magnetic disk drive) is the smallest unit of storage that the DOS operating system supports. In particular, a logical block or sector (referred to herein as a logical block) has come to be defined as 512-bytes of information for DOS and most other operating systems in existence. 
         [0015]    As an alternative to magnetic hard drive implementations, semiconductor non-volatile memory devices, such as Flash memories, have become ubiquitous. Flash and other non-volatile memory systems that emulate the storage characteristics of hard disk drives are preferably similarly structured to support storage in, by way of example and not limitation, 512-byte blocks along with additional storage for overhead associated with mass storage, such as ECC bits, status flags for the sector or erasable block, and/or redundant bits. In the present invention of Flash memory device implementations, the controller and/or software routines additionally allow the Flash memory device or a memory subsystem of Flash memory devices to appear as a read/write mass storage device (i.e., a magnetic disk) to the host by conforming the interface of the Flash memory device to be compatible with a standard interface for a conventional magnetic hard disk drive. This approach allows the Flash memory device to appear to the operating system as a block read/write mass storage device or disk. 
         [0016]    By way of example, at least one such interface has been codified by the Personal Computer Memory Card International Association (PCMCIA), Compact Flash (CF), and Multimedia Card (MMC) standardization committees, which have each promulgated a standard for supporting Flash memory systems or Flash memory “cards” with a hard disk drive protocol. A Flash memory device or Flash memory card (including one or more Flash memory array chips) whose interface meets these standards can be plugged into a host system having a standard DOS or compatible operating system with a Personal Computer Memory Card International Association-Advanced Technology Attachment (PCMCIA-ATA) or standard ATA interface. Other additional Flash memory based mass storage devices of differing low level formats and interfaces also exist, such as Universal Serial Bus (USB) Flash drives. As used herein, “Flash memory” includes various known forms of non-volatile memory including without limitation NAND and NOR based non-volatile memory arrays. 
         [0017]      FIG. 1  is a simplified diagram of an embodiment of an electronic system  100  that incorporates a Flash memory device  104 , in accordance with the present invention. In the system  100  of  FIG. 1 , the Flash memory device  104  is coupled to a processor  102  with an address/data bus  106 . Internal to the Flash memory device  104 , a controller or a control state machine  110  directs internal operation of the Flash memory device  104 , including managing the Flash memory array  108 . The Flash memory array  108  contains floating gate memory cells arranged in a sequence of erasable blocks  116 ,  118 . Electronic system  100  may comprise, for example, computational and communication devices such as a computer, a cellular telephone, a personal digital assistant, an MP3 player, a digital camera, or other such devices that may find application to editing a stored file. 
         [0018]    According to non-volatile memory devices in general, and Flash memory devices in particular, all the cells in an erasable block are generally erased all at once since a memory cell within an erasable block cannot be directly rewritten without first engaging in a block erase operation. The execution of erasable block management is typically under the control of the internal controller or control state machine, an external memory controller, or software driver through a provided abstraction layer allowing the non-volatile device to appear as a freely rewriteable device. Other internal block management features (not shown) include the logical address to physical address translation mapping with the translation layer, the assignment of erased and available erasable blocks for utilization, and scheduling for block erasure the erasable blocks that have been used and closed out. Erasable block management may also allow for load leveling of the internal floating gate memory cells to help prevent write fatigue failure. Write fatigue is where the floating gate memory cell, after repetitive writes and erasures, no longer properly erases and removes charge from the floating gate. Load leveling procedures increase the mean time between failure of the erasable block and non-volatile/Flash memory device as a whole. 
         [0019]    Two common types of Flash memory array architectures are the “NAND” and “NOR” architectures. Other types of non-volatile memory include, but are not limited to, Polymer Memory, Ferroelectric Random Access Memory (FeRAM), Ovionics Unified Memory (OUM), Nitride Read Only Memory (NROM), and Magnetoresistive Random Access Memory (MRAM). 
         [0020]    In the NOR Flash memory array architecture, the floating gate memory cells of the memory array are arranged in a matrix. The gates of each floating gate memory cell of the array matrix are connected by rows to word select lines (word lines) and their drains are connected to column bit lines. The source of each floating gate memory cell is typically connected to a common source line. The NOR architecture floating gate memory array is accessed by a row decoder activating a row of floating gate memory cells by selecting the word line connected to their gates. The row of selected memory cells then place their stored data values on the column bit lines by flowing a differing current if in a programmed state or not programmed state from the connected source line to the connected column bit lines. 
         [0021]    A NAND Flash memory array architecture also arranges its array of floating gate memory cells in a matrix such that the gates of each floating gate memory cell of the array are connected by rows to word lines. However each memory cell is not directly connected to a source line and a column bit line. Instead, the memory cells of the array are arranged together in strings, typically of 8, 16, 32 or more each, where the memory cells in the string are connected together in series, source to drain, between a common source line and a column bit line. The NAND architecture floating gate memory array is then accessed by a row decoder activating a row of floating gate memory cells by selecting the word select line connected to their gates. In addition, the word lines connected to the gates of the unselected memory cells of each string are also driven. However, the unselected memory cells of each string are typically driven by a higher gate voltage so as to operate them as pass transistors and allowing them to pass current in a manner that is unrestricted by their stored data values. Current then flows from the source line to the column bit line through each floating gate memory cell of the series connected string, restricted only by the memory cells of each string that are selected to be read. Thus, the current encoded stored data values of the row of selected memory cells are placed on the column bit lines. 
         [0022]    In  FIG. 1 , each erasable block  116 ,  118  contains a series of physical pages or rows  120 , each page/row containing physical storage for one or more logical sectors or blocks  124  (shown here for illustration purposes as a single logical sector/block  124  per physical page/row  120 ) that contain a user data space and a control/overhead data space. The overhead data space contains overhead information for operation of the logical block  124 , such as an error correction code (not shown), status flags, or an erasable block management data field area (not shown). The user data space in each logical block  124  is typically 512 bytes long. It is noted that other interfaces (not shown) to the Flash memory device  104  and formats for the erasable blocks  116 ,  118 , physical pages  120 , and logical sectors/blocks  124  are possible and should be apparent to those of ordinary skill in the art. It is also noted that additional Flash memory devices  104  may be incorporated into the system  100  as required. 
         [0023]      FIGS. 2A and 2B  detail encoding  200 ,  220  of user data into sector/logical blocks of a Flash memory array. In  FIG. 2A , user data  212  and header/overhead data  214  are shown in a memory array  202 , which includes erasable blocks  116 ,  118  ( FIG. 1 ), where a single 512-byte logical block is encoded in each physical page/row  210  of the memory array  202 . The memory array  202  contains a series of pages/rows  210 , each row containing a logical block having a user data area  204  and an overhead data area  206 . 
         [0024]    In  FIG. 2B , user data  226  and header/overhead data  228  are shown in a memory array  222 , which includes erasable blocks  116 ,  118  as illustrated in  FIG. 1 , where multiple logical blocks  232  are encoded in each physical page/row  230  of the memory array  222 . As stated above, many memories support multiple logical sectors or logical block  232  within a single physical page/row  230 . In particular, NAND architecture Flash memories typically utilize this approach due to their generally higher memory cell density and larger page/row sizes. The memory page/row  230  contains multiple logical blocks/sectors  232 , each logical block  232  having a user data area  226  and an overhead data/block header section  228 . 
         [0025]    In the embodiment illustrated in  FIG. 2B , the page/row  230  contains 2112 bytes of data (4×512 bytes user data+4×8 bytes ECC+32 bytes for overhead) and is formatted to contain four logical blocks  232  having a user data area  226  of 512-bytes each. The four logical sectors  232  are typically sequentially addressed N, N+1, N+2, and N+3, where N is a base logical sector address for the page/row  230 . It is noted that the pages/rows  210  and  230  of  FIGS. 2A and 2B  are for illustration purposes and that other page/row sector formats of differing data sizes, numbers of logical blocks/sectors, and relative positioning of sectors are possible. 
         [0026]    As stated above, in an erasable block based non-volatile memory, the memory array is divided into a plurality of individually erasable groups of memory cells called erasable blocks, which are each typically further divided into a plurality of 512-byte physical blocks. Before use, the non-volatile memory is formatted to conform to the data structures and management data fields/tables of the file system or memory structure being represented. Each physical block of the memory array also may contain a header or overhead data area that typically includes various data used in the management of the physical block. This management data can include such items as the status of the physical block (valid, erased/available, or to be erased/invalid) and an error correction code (ECC) for the data of the logical block. In addition, the header typically also includes an identifier that identifies the logical block address for the physical block. 
         [0027]    As previously stated, the translation layer in conjunction with the erasable block management (not shown) manages the storage of logical blocks in non-volatile memory devices or a non-volatile memory subsystem. The client of a translation layer is typically the file system or operating system of an associated host system or processor. The translation layer (not shown) allows the non-volatile memory to appear as a freely rewriteable device or magnetic disk/hard drive, allowing the client to read and write logical blocks to the non-volatile memory. 
         [0028]      FIG. 3  is a memory map of a Flash memory array partitioned according to a file system, in accordance with one or more of the various embodiments of the present invention. In  FIG. 3 , a Flash memory array may be partitioned into one or more partitions. For clarity, a single partition  126  is illustrated and includes a system area  128  and a data area  130 . System area  128  has various segments including, for example, the master boot record (“MBR”) area  132 , partition boot record (“PBR”) area  134 , FAT1 area  136 , FAT2 area  138  and root directory area  140 . 
         [0029]    MBR area  132  stores overall partition information, including instructions to jump from MBR area  132  to PBR area  134  if the media is a bootable device. MBR area  132  may also include a hidden area that is a reserved space (not shown) between MBR area  132  and PBR area  134 . 
         [0030]    PBR area  134  includes partition/boot information for a partition. For example, PBR area  134  includes information for the type of FAT (e.g., FAT12/16/32 bits depending on the FAT standard implemented, such as, respectively, FAT12, FAT16 or FAT32) a label (i.e., name of the drive), size of the drive; cluster size (i.e., the number of sectors per allocation unit) number of FAT areas (e.g., FAT 1 area and FAT 2 area) and the number of sectors per FAT. 
         [0031]    FAT1 and FAT2 areas  136 ,  138  contain cluster information for each file. For example, in a FAT12 file system, each entry in FAT1 and FAT2 areas  136  and  138  contains 12 bits and there are a total of 4096 entries. Clusters 0 and 1 are reserved for 0xFFFFF8 (for media type) and End of Cluster. A particular cluster (e.g., cluster 4087) is used to indicate bad clusters. For example, in a FAT16 file system, each entry contains 16 bits and, for example, in a FAT32 file system, each entry contains 32 bits. 
         [0032]    Root directory area  140  contains entries for each file. Each directory entry includes a certain number of bytes for file name or directory (e.g., 8 bytes), a number of bytes for extension (e.g., 3 bytes), a number of bytes (e.g., 1 byte) for file attributes (e.g., if a file is read only, hidden, system file, volume label, directory or modified), a number of bytes indicating the time and date when a file was created, a certain number of bytes (e.g., 2) for a starting cluster, and a certain number of bytes (e.g., 4) indicating the file length. 
         [0033]    The number of bytes for the starting cluster points to the first cluster in the FAT and the last cluster may be indicated by 0xFFF, 0xFFFF or 0xFFFFFF. In order to write a file name in the directory, the host system finds free cluster space in FAT1 area  136  and data is written in data area  130 , including erasable blocks  116 ,  118  ( FIG. 1 ). Entries in both the FAT1 area  136  and the FAT2 area  138  are then updated. The directory entry (e.g., the date/time/starting cluster/file length) is also updated. 
         [0034]    As stated, the root directory area  140  is a table of, for example, 32-byte entries that each set forth certain attributes of a file. Typically, each directory entry making up the root directory in the root directory area  140  includes a file name, a file extension, attribute flags, time and date stamps for the file, the starting cluster number for the clusters that make up the file, and the file size. 
         [0035]    Each file on the Flash memory device  104  ( FIG. 1 ) is made up of one or more clusters. The file allocation table (FAT) located in the FAT1 and FAT2 areas  136 ,  138  contains a record in the form of a chain identifying how the clusters making up the file are linked together. A typical FAT contains a list of two-byte entries, one for each cluster. For some prior FATs, the FAT entries are longer than two bytes. The length of each FAT entry depends upon the total number of clusters. The directory entry in the root directory area  140  for a file contains the starting cluster number for that file, and the host system, such as processor  102  of  FIG. 1 , uses that starting cluster number to access the FAT. Each FAT entry is a pointer to the next cluster of the file. Thus, the FAT entry retrieved by a first access contains the cluster number of the next cluster making up the file. The host system, such as processor  102  of  FIG. 1 , uses that next cluster number to access the FAT to retrieve yet another cluster number, and continues this process until the end of the file is reached. 
         [0036]    When a file is being written or programmed into Flash memory array  108  ( FIG. 1 ), there exists an opportunity for the power to the memory device to be interrupted, resulting in an incomplete record of the chain of clusters identifying the file. While such interruptions may be reduced by physical locks or other preventive mechanisms, such mechanisms defeat the desirable portability and ease of configurability of Flash memory devices. The various embodiments of the present invention provide a mechanism to reduce the window of opportunity for creating errors in the chain of cluster as recorded in the FAT during an update or edit to an existing file. 
         [0037]      FIGS. 4 and 5  illustrate an edit to an existing file in accordance with a file system.  FIG. 4  illustrates an existing file  402  stored in a file system  400 . As stated, an indicia of an existing file  402  is stored in the root directory area  140  of the system area  128  as described with respect to  FIG. 3 . Included in the root directory area  140  may be a file name, a file extension, attribute flags, time and date stamps for the file, the file size, and the starting cluster number or pointer  412  for the clusters that make up the file  402 . 
         [0038]    A location  406  in the FAT  404  is pointed to by the root directory entry for the file  402 . Location  406  corresponds to a cluster sector page  408  (used herein interchangeably depending upon the specific defined structure of the file system  400 ) of erasable block  410 . Location  406  in the FAT  404  further includes a next cluster number or pointer  414 , which corresponds, by way of example, to cluster  416  of erasable block  418 . 
         [0039]    A location  420  in the FAT  404  is pointed to by the next cluster number or pointer  414  for the file  402 . Location  420  corresponds to a cluster  416  of erasable block  418 . Location  420  in the FAT  404  further includes a next cluster number or pointer  422 , which corresponds, by way of example, to cluster  424  of erasable block  426 . A location  428  in the FAT  404  includes an end-of-file indicator indicating that no more clusters are to be included in the file  402 . As illustrated, file  402  includes clusters  408 ,  416 ,  424  from, for example, the respective erasable blocks  410 ,  418 ,  426 . 
         [0040]      FIG. 5  illustrates an edit or update occurring to a file, illustrated as edited file  402 ′. It is recalled that the clusters or pages of the non-volatile memories as described herein are not rewriteable until the entire erasable block has been reclaimed by erasing or resetting the non-volatile memory cells within the block. Accordingly,  FIG. 5  illustrates an edit to cluster  408  in file system  400 ′, which is rewritten at a new location in the Flash memory array as cluster  408 ′ in the erasable block  410 ′. It is noted that the edited file  402 ′ is correctly composed of clusters  408 ′,  416 ,  424 ; however, FAT  404  has not yet been updated by redirecting starting cluster or pointer number  412  from pointing to location  406  to location  430  to reflect the relocation of amended cluster  408 ′ in erasable block  410 ′. If power to the memory device is interrupted prior to the completion of the change to the FAT, the edited file  402 ′ may become corrupt and unusable. 
         [0041]      FIGS. 6A-6D  illustrate an editing process of a file in a Flash memory device, in accordance with an embodiment of the present invention.  FIG. 6A  illustrates an edit to an existing file in a file system. An existing file  502  is stored in a file system  500 . As stated, an indicia of an existing file  502  is stored in the root directory area  140  of the system area  128  as described with respect to  FIG. 3 . Included in the root directory area  140  may be a file name, a file extension, attribute flags, time and date stamps for the file, the file size, and the starting cluster number or pointer  512  for the clusters that make up the file  502 . 
         [0042]    A location  506  in the FAT  504  is pointed to by the root directory entry for the file  502 . Location  506  corresponds to a cluster sector page  508  (used herein interchangeably depending upon the specific defined structure of the file system  500 ) of erasable block  510 . Location  506  in the FAT  504  further includes a next cluster number or pointer  514 , which corresponds, by way of example, to cluster  516  of erasable block  518 . 
         [0043]    A location  520  in the FAT  504  is pointed to by the next cluster number or pointer  514  for the file  502 . Location  520  corresponds to a cluster  516  of erasable block  518 . Location  520  in the FAT  504  further includes a next cluster number or pointer  522 , which corresponds, by way of example, to cluster  524  of erasable block  526 . A location  528  in the FAT  504  includes the last cluster in response to the end of the file  502 . As illustrated, file  502  includes clusters  508 ,  516 ,  524  from, for example, the respective erasable blocks  510 ,  518 ,  526 . 
         [0044]      FIG. 6B  illustrates a further act in the editing of a file, in accordance with an embodiment of the present invention. A file copy  602  of existing file  502  to be edited is created leaving the original unedited file  502  and the corresponding respective FAT entries intact during the editing process. The file copy  602  is stored in a file system  500 . A location  606  in the FAT  504  is pointed to by a starting cluster or number  612  for the file copy  602 . Location  606  corresponds to a cluster sector page  608  of erasable block  510 . Location  606  in the FAT  504  further includes a next cluster number or pointer  614 , which corresponds, by way of example, to cluster  616  of erasable block  510 . 
         [0045]    A location  620  in the FAT  504  is pointed to by the next cluster number or pointer  614  for the file copy  602 . Location  620  corresponds to a cluster  616  of erasable block  510 . Location  620  in the FAT  504  further includes a next cluster number or pointer  622 , which corresponds, by way of example, to cluster  624  of erasable block  510 . A location  628  in the FAT  504  includes an end-of-file indicator indicating that no more clusters are to be included in the file copy  602 . As illustrated, file copy  602  includes clusters  608 ,  616 ,  624  from, for example, the erasable block  510 . It should be noted that the locations of the clusters within specific erasable blocks is merely illustrative and other arrangements are also contemplated. 
         [0046]      FIG. 6C  illustrates a further act in the editing of a file, in accordance with an embodiment of the present invention. During the file editing process, the edits are performed on the file copy  602 . As previously described, the clusters or pages of the non-volatile memories as described herein are not rewriteable until the entire erasable block has been reclaimed by erasing or resetting the non-volatile memory cells within the block. During the editing process, one or more of the clusters  608 ,  616 ,  624  associated with the file copy are altered. By way of illustration, the data in a cluster  608 , which is the copy of cluster  508 , is subjected to alterations. The altered data is written into cluster  608 ′ in the erasable block  518 . It is noted that the edited file copy  602 ′ is correctly composed of clusters  608 ′,  616 ,  624 . 
         [0047]    As noted previously, one of the vulnerabilities of editing files in Flash memory devices is the untimely interruption of power to the memory device prior to all of the entries in the file allocation table being correctly written or prior to all of the clusters associated with the edited file being correctly written into the Flash memory array. With reference to the editing process described to this point as described with reference to  FIGS. 6A-6C , the occurrence of a power interruption during either the creation of the file copy  602 , or the editing of data stored in cluster  608 ′, or the reassociation of the location (e.g., location  606  from cluster  608  to cluster  608 ′) of the next cluster in the file allocation table, would not result in the corruption of the original file  502  even though the edits may have been lost. 
         [0048]    The various embodiments of the present invention narrow the window of vulnerability of the files being corrupted during inadvertent power interruption by performing the editing on a copy of the original file while maintaining the root directory and FAT pointing to the original file in the Flash memory array. Should power interruption occur in any of these states, the original file remains uncorrupted on power up. 
         [0049]    As a further act in the editing process in accordance with the various embodiments of the present invention, the starting cluster number or pointer  512  in the root directory entry for file  502  is reconfigured to point to location  606  in the FAT  504 . The window of vulnerability of corruption of a file stored in the Flash memory array has, thus, been greatly narrowed down to power interruption occurring during the reconfiguration of the addressing of the single starting cluster in the root directory rather than during either the writing of data into clusters in the Flash memory array or the updating of the FAT. 
         [0050]    The processes and devices described above illustrate embodiments of methods and devices out of many that may be used and produced according to the present invention. The above description and drawings illustrate embodiments that provide significant features and advantages of the present invention. It is not intended, however, that the present invention be strictly limited to the above-described and illustrated embodiments. 
         [0051]    Although the present invention has been shown and described with reference to particular embodiments, various additions, deletions and modifications that will be apparent to a person of ordinary skill in the art to which the invention pertains, even if not shown or specifically described herein, are deemed to lie within the scope of the invention as encompassed by the following claims.