Mobi 90

[Hadda Condino]

Thealuminum frame and stainless steel parts are corrosion free from salt water. The floatable wheels and armrests provide an unprecedented experience due to their stable buoyant design. The Mobi-Chair Floating Beach Wheelchair is suitable for use at the beach and in swimming pools.

Mobi-Chair Floating Beach Wheelchair provides a comfortable ride. The rubber pneumatic tires absorb the shock and discomfort caused by rugged terrain, and it provides easy mobility through sand and other rough surfaces.

The armrests and wheels are comprised of buoyant materials that enable balance while bathing in the water. The integrated handles on the armrests provide added stability while enjoying the ride on land or in the water.

Transportation and storage is convenient. Mobi-Chair Floating Beach Wheelchair is quickly assembled or disassembled by operating the quick release pins and joints without tools. It can easily fit into any vehicle.

MOBI is the name given to the format developed for the MobiPocket Reader. It is currently used by Amazon with a slightly different DRM scheme and called AZW. Amazon uses this extension for files created by KindleGen even though they actually have both a MOBI format, sometimes called KF7, and a KF8 format inside the same file.

MOBI is the format used by the MobiPocket Reader and Amazon Kindle Readers. It may have a .mobi extension or it may have a .prc extension. The extension can be changed by the user to either of the accepted forms. In either case it may be DRM protected or non-DRM. The .prc extension is used because the PalmOS doesn't support any file extensions except .prc or .pdb. Note that Mobipocket prohibits their DRM format to be used on dedicated eBook readers that support other DRM formats. Mobi source files are based on the OEB, Open eBook standard.

From time to time features have been added to the format so new files may have problems if you try to read them with a down level reader. Currently the source files follow the guidelines in the Open eBook format.

Like PalmDOC, the Mobipocket file format is that of a standard Palm Database Format file. The header of that format includes the name of the database (usually the book title and sometimes a portion of the authors name) which is up to 31 bytes of data. The files are identified as Creator ID of MOBI and a Type of BOOK.

The old Mobipocket Encryption scheme only allows the file to be registered with one PID, unlike the current encryption scheme that allows multiple PIDs to be used in a single file. Unless specifically mentioned, all the encryption information on this page refers to the current scheme.

Most Mobipocket file also have a MOBI header in record 0 that follows these 16 bytes, and newer formats also have an EXTH header following the MOBI header, again all in record 0 of the PDB file format.

If the MOBI header indicates that there's an EXTH header, it follows immediately after the MOBI header. Since the MOBI header is of variable length, this isn't at any fixed offset in record 0. Note that some readers will ignore any EXTH header info if the mobipocket version number specified in the MOBI header is 2 or less (perhaps 3 or less).

There are lots of different EXTH Records types. Ones found so far in Mobipocket files are listed here, with possible meanings. Hopefully the table will be filled in as more information comes to light.

The name is followed by two null bytes, and then padded with null bytes to a four-byte boundary. For example, if the name is 16 bytes long, with two null bytes, that makes 18 bytes, and it then gets another two null bytes added to make it up to 20 bytes in total. However, the length stored in the header is only 16. If the name was 19 bytes, it would be followed by two null bytes to make it up to 21 bytes, and then padded with three more null bytes to make it up to 24 bytes.

The TAGX section follows the INDX header and is essential for decoding the index values, as it defines which how many control bytes an entry contains, which bits correspond to which tag and how many values a tag requires (most tag need one value, but some have two, maybe more).

The tag table entries are multiple of 4 bytes. The first byte is the tag, the second byte the number of values, the third byte the bit mask and the fourth byte indicates the end of the control byte. If the fourth byte is 0x01, all other bytes of the entry are zero.

Some parts of the Mobipocket format encode data as variable-width integers. These integers are represented big-endian with 7 bits per byte in bits 1-7. They may be either forward-encoded, in which case only the LSB has bit 8 set, or backward-encoded, in which case only the MSB has bit 8 set. For example, the number 0x11111 would be represented forward-encoded as:

The Extra Data Flags field of the MOBI header indicates which, if any, trailing entries are appended to the end of each text record. Each set bit in the field indicates a trailing entry. The entries appear to occur in bit-order; e.g., trailing entry 1 immediately follows the text content and entry 16 occurs at the very end of the record. The effect and exact details of most of these entries is unknown. The trailing entries indicated by bits 2-16 appear to follow a common format. That format is:

When bit 1 of the Extra Data Flags field is set, each record is followed by a trailing entry containing any extra bytes necessary to complete a multibyte character which crosses the record boundary. The bytes do not participate in compression regardless which compression scheme is used for the file. However, unlike the trailing data bytes, the multibytes (including the count byte) do get included in any encryption. The overlapping bytes then re-appear as normal content at the beginning of the following record. The trailing entry ends with a byte containing a count of the overlapping bytes plus additional flags.

PalmDOC uses LZ77 compression techniques, an implementation for PalmDOC can be found at Github . DOC files can contain only compressed text. The format does not allow for any text formatting. This keeps files small, in keeping with the Palm philosophy. However, extensions to the format can use tags, such as HTML or PML, to include formatting within text. These extensions to PalmDoc are not interchangeable and are the basis for most eBook Reader formats on Palm devices.

LZ77 algorithms achieve compression by replacing portions of the data with references to matching data that has already passed through both encoder and decoder. A match is encoded by a pair of numbers called a length-distance pair, which is equivalent to the statement "each of the next length characters is equal to the character exactly distance characters behind it in the uncompressed stream." (The "distance" is sometimes called the "offset" instead.)

In the PalmDoc format, a length-distance pair is always encoded by a two-byte sequence. Of the 16 bits that make up these two bytes, 11 bits go to encoding the distance, 3 go to encoding the length, and the remaining two are used to make sure the decoder can identify the first byte as the beginning of such a two-byte sequence. The exact algorithm needed to decode the compressed text can be found on the PalmDOC page.

PalmDOC data is always divided into 4096 byte blocks (uncompressed size) and the blocks are acted upon independently; no information from previous or later blocks is needed when a block is being compressed or decompressed.

PalmDOC does have support for bookmarks. These pointers are named and refer to an offset location in a file. If the file is edited these locations may no longer refer to the correct locations. Some reading programs allow the user to enter or edit these bookmarks while others treat them as a TOC. Some reading programs may ignore them entirely. They are stored at the end of the file itself so the full file needs to be scanned when loaded to find them.

If the file contains images, they follow the text blocks, with each image using a single block. The 4096-byte record size in the PalmDoc header applies only to text records; image records may be larger.

In some cases, MobiPocket Creator adds a 2-zero-byte record after the text records in a file. This record is not included in the "record count" of text records in the PalmDoc header, and is also not used as the "first non-book index" in the MOBI header. (If the 2-zero-byte record is present, the index of the following block is used as the "first non-book index".)

MobiPocket Creator also ends files with three records: 'FLIS', 'FCIS', and 'end-of-file', in that order. The 'FLIS' and 'FCIS' records do not seem to be necessary for MobiPocket Reader or the Amazon Kindle 2 to read the file. The 'end-of-file' record might be necessary.

MOBI files created with Mobipocket creator, Amazon's Personal Document Service, or Kindle Direct Publishing (former Amazon DTP) don't include SRCS record. In a past, kindlegen had an undocumented option to suppress this record, but the option was removed in 2010.

A SRCS record is a record whose content is a zip archive of all source files (i.e., .opf, .ncx, .htm, .jpg, ...) given to the command and puts it in the generated MOBI file. The record begins with the "SRCS" signature and looks as follows:

This is the extension used on a side file (auxiliary) for MOBI formatted eBooks. It is used to store metadata used by the library software and also to store user entered data like bookmarks, annotations, last read position. This file is created automatically by the reader program when the eBook is first opened and has a .mbp extension. The Library management software in MobiPocket uses this file to get information displayed in the library window such as title, author, and description so that it won't have to open the larger eBook file.

There are several ways to create eBooks in the MOBI format. The rules for the format of the source files need to create eBooks in MOBI are spelled out in documents on the MobiPocket web site. The recommended tool called MobiPocket Creator is available as a downloadfrom the web site.

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