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Computer File

Computer files definition of field 008/18-34 is used when Leader/06 (Type of record) contains code m. Field 008 positions 01-17 and 35-39 are defined the same in all 008 fields and are described in the 008-All materials section.

computer file

Field 008/18-34 correspond to equivalent positionally defined data elements in field 006/01-17 when field 006/00 (Form of material) contains code m (Computer file/Electronic resource). Details about specific codes defined for the equivalent character positions in field 006 and 008 for computer files are provided in the Guidelines for Applying Content Designators section of 008-Computer files only.

Ordered set of instructions directing the computer to perform basic operations and identifying the information and mechanisms required. Includes videogames and microcomputer software and computer models. Some types of computer programs (e.g., game, font) are identified by separate codes in this character position.

Supports navigation through and manipulation of many kinds of media (i.e., audio, video, etc.). Interactive multimedia usually gives the user a high level of control, often allowing almost conversational interaction with the computer and data.

May contain nonbibliographic information. An online system or service supports system-based user interaction. If the focus of the record is to describe the system itself, with the content of the databases incidental contained therein, it is coded here. If the resource is an online file where the system is incidental to the description, it falls into another category. Examples of online systems or services are: online library systems (consisting of a variety of databases), FTP sites, electronic bulletin boards, network information centers.

One-character alphabetic code that indicates whether the computer file is published or produced by or for an international, national, provincial, state, or local government agency (including intergovermental bodies of all types), any subdivision of such a body and, if so, the jurisdictional level of the agency.

A computer file is a computer resource for recording data in a computer storage device, primarily identified by its file name. Just as words can be written to paper, so can data be written to a computer file. Files can be shared with and transferred between computers and mobile devices via removable media, networks, or the Internet.

Different types of computer files are designed for different purposes. A file may be designed to store an Image, a written message, a video, a computer program, or any wide variety of other kinds of data. Certain files can store multiple data types at once.

"File" was used in the context of computer storage as early as January 1940. In Punched Card Methods in Scientific Computation,[2] W. J. Eckert stated, "The first extensive use of the early Hollerith Tabulator in astronomy was made by Comrie.[3] He used it for building a table from successive differences, and for adding large numbers of harmonic terms". "Tables of functions are constructed from their differences with great efficiency, either as printed tables or as a file of punched cards."

In early use, the underlying hardware, rather than the contents stored on it, was denominated a "file". For example, the IBM 350 disk drives were denominated "disk files".[6] The introduction, circa 1961, by the Burroughs MCP and the MIT Compatible Time-Sharing System of the concept of a "file system" that managed several virtual "files" on one storage device is the origin of the contemporary denotation of the word. Although the contemporary "register file" demonstrates the early concept of files, its use has greatly decreased.

On some platforms the format is indicated by its filename extension, specifying the rules for how the bytes must be organized and interpreted meaningfully. For example, the bytes of a plain text file (.mw-parser-output .monospacedfont-family:monospace,monospace.txt in Windows) are associated with either ASCII or UTF-8 characters, while the bytes of image, video, and audio files are interpreted otherwise. Most file types also allocate a few bytes for metadata, which allows a file to carry some basic information about itself.

Some file systems can store arbitrary (not interpreted by the file system) file-specific data outside of the file format, but linked to the file, for example extended attributes or forks. On other file systems this can be done via sidecar files or software-specific databases. All those methods, however, are more susceptible to loss of metadata than container and archive file formats.

At any instant in time, a file has a specific size, normally expressed as a number of bytes, that indicates how much storage is occupied by the file. In most modern operating systems the size can be any non-negative whole number of bytes up to a system limit. Many older operating systems kept track only of the number of blocks or tracks occupied by a file on a physical storage device. In such systems, software employed other methods to track the exact byte count (e.g., CP/M used a special control character, Ctrl-Z, to signal the end of text files).

The general definition of a file does not require that its size have any real meaning, however, unless the data within the file happens to correspond to data within a pool of persistent storage. A special case is a zero byte file; these files can be newly created files that have not yet had any data written to them, or may serve as some kind of flag in the file system, or are accidents (the results of aborted disk operations). For example, the file to which the link /bin/ls points in a typical Unix-like system probably has a defined size that seldom changes. Compare this with /dev/null which is also a file, but as a character special file, its size is not meaningful.

The way information is grouped into a file is entirely up to how it is designed. This has led to a plethora of more or less standardized file structures for all imaginable purposes, from the simplest to the most complex. Most computer files are used by computer programs which create, modify or delete the files for their own use on an as-needed basis. The programmers who create the programs decide what files are needed, how they are to be used and (often) their names.

In some cases, computer programs manipulate files that are made visible to the computer user. For example, in a word-processing program, the user manipulates document files that the user personally names. Although the content of the document file is arranged in a format that the word-processing program understands, the user is able to choose the name and location of the file and provide the bulk of the information (such as words and text) that will be stored in the file.

Many applications pack all their data files into a single file called an archive file, using internal markers to discern the different types of information contained within. The benefits of the archive file are to lower the number of files for easier transfer, to reduce storage usage, or just to organize outdated files. The archive file must often be unpacked before next using.

Files on a computer can be created, moved, modified, grown, shrunk (truncated), and deleted. In most cases, computer programs that are executed on the computer handle these operations, but the user of a computer can also manipulate files if necessary. For instance, Microsoft Word files are normally created and modified by the Microsoft Word program in response to user commands, but the user can also move, rename, or delete these files directly by using a file manager program such as Windows Explorer (on Windows computers) or by command lines (CLI).

In Unix-like systems, user space programs do not operate directly, at a low level, on a file. Only the kernel deals with files, and it handles all user-space interaction with files in a manner that is transparent to the user-space programs. The operating system provides a level of abstraction, which means that interaction with a file from user-space is simply through its filename (instead of its inode). For example, rm filename will not delete the file itself, but only a link to the file. There can be many links to a file, but when they are all removed, the kernel considers that file's memory space free to be reallocated. This free space is commonly considered a security risk (due to the existence of file recovery software). Any secure-deletion program uses kernel-space (system) functions to wipe the file's data.

When moving files between devices or partitions, some file managing software deletes each selected file from the source directory individually after being transferred, while other software deletes all files at once only after every file has been transferred.

With the mv command for instance, the former method is used when selecting files individually, possibly with the use of wildcards (example: mv -n sourcePath/* targetPath, while the latter method is used when selecting entire directories (example: mv -n sourcePath targetPath). Microsoft Windows Explorer uses the former method for mass storage filemoves, but the latter method using Media Transfer Protocol, as described in Media Transfer Protocol File move behaviour.

The former method (individual deletion from source) has the benefit that space is released from the source device or partition imminently after the transfer has begun, meaning after the first file is finished. With the latter method, space is only freed after the transfer of the entire selection has finished.

If an incomplete file transfer with the latter method is aborted unexpectedly, perhaps due to an unexpected power-off, system halt or disconnection of a device, no space will have been freed up on the source device or partition. The user would need to merge the remaining files from the source, including the incompletely written (truncated) last file.

With the individual deletion method, the file moving software also does not need to cumulatively keep track of all files finished transferring for the case that a user manually aborts the file transfer. A file manager using the latter (afterwards deletion) method will have to only delete the files from the source directory that have already finished transferring. 041b061a72

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