Binary file transfer (BFT) describes the syntax and semantics required to represent data files that are transferred using fax modems. Binary file transfer is a standard used to transmit data files through protocols of different telematic services, including Telefax Group 3 and 4, Teletex and Data Transfer and Manipulation (DTAM) normal mode.
Binary files hold data types encoded in binary form for computer processing and storage. Binary files are made up of byte sequences where the binary digits are grouped in eights. They may contain text, images and compressed versions of other files or sounds. A few binary files have headers within them. If they do not contain headers, they are called flat binary files.
In order to transfer binary files through systems that do not permit certain data values, they have to be translated into plain text format. Such a translation increases the file size by 30 percent. Files are translated back into binary after being received at the destination.
Transmitted binary data messages consist of sequences of certain attributes, which include the file data itself. The sequence of the name component is the file name of type graphic string. If more than one element is encoded, the first element is the file name and the remaining elements represent file name prefixes. Another attribute, called the permitted action attribute, defines the set of actions performed on the file. These include read, insert, replace, extend, erase, etc.
The content type attribute contains the abstract data type of the file contents and the structuring information necessary for maintaining the complete file structure and the semantics during the binary file transfer. The storage account attribute denotes the authority responsible for accumulated file storage charges. The value of the storage account attribute is of type graphic string. Date and time attributes indicate the time when the file was created. The value of this attribute type is generalized time. Date and time related to the last modification attribute indicate when the file contents were last modified. The recipient attribute indicates the final user destination of the binary file transfer. The character set attribute indicates the international character set to be used for rendering the character data included in the attribute data-file content. The compression attribute indicates an optional compression added to the contents of the data-file content. The access control syntax defines conditions under which access to the file is valid.
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