C++ Read Data From File Separated by Two Points

Estimator resource

This commodity is about computer files and file systems in general terms. For a more detailed and technical article, see File system.

A estimator file is a computer resources for recording data in a computer storage device, primarily identified by its file name. Just as words can be written to paper, so tin data exist 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 figurer files are designed for different purposes. A file may be designed to shop an Image, a written message, a video, a computer plan, or any wide variety of other kinds of data. Certain files can shop multiple information types at one time.

By using figurer programs, a person tin can open, read, change, salvage, and close a computer file. Reckoner files may be reopened, modified, and copied an arbitrary number of times.

Files are typically organized in a file system, which tracks file locations on the disk and enables user admission.

Etymology [edit]

The give-and-take "file" derives from the Latin filum ("a thread").^[i]

"File" was used in the context of figurer storage as early as January 1940. In Punched Card Methods in Scientific Computation,^[2] West. J. Eckert stated, "The start extensive apply 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 big numbers of harmonic terms". "Tables of functions are synthetic from their differences with great efficiency, either equally printed tables or as a file of punched cards."

In February 1950, in a Radio Corporation of America (RCA) advertizement in Pop Scientific discipline magazine^[4] describing a new "retention" vacuum tube it had developed, RCA stated: "the results of endless computations tin exist kept 'on file' and taken out once again. Such a 'file' at present exists in a 'retentiveness' tube developed at RCA Laboratories. Electronically it retains figures fed into calculating machines, holds them in storage while it memorizes new ones – speeds intelligent solutions through mazes of mathematics."

In 1952, "file" denoted, amid other things, information stored on punched cards.^[5]

In early on 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 organization" 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 employ has greatly decreased.

File contents [edit]

On most modern operating systems, files are organized into one-dimensional arrays of bytes. The format of a file is divers by its content since a file is solely a container for data.

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 obviously text file (.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 likewise allocate a few bytes for metadata, which allows a file to behave some basic information nearly itself.

Some file systems can store capricious (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 annal file formats.

File size [edit]

At any instant in time, a file accept a size, normally expressed equally number of bytes, that indicates how much storage is associated with the file. In virtually modern operating systems the size tin be any non-negative whole number of bytes up to a system limit. Many older operating systems kept track merely of the number of blocks or tracks occupied past a file on a physical storage device. In such systems, software employed other methods to track the exact byte count (east.k., CP/Thousand used a special control graphic symbol, Ctrl-Z, to signal the end of text files).

The full general definition of a file does not require that its size accept any real significant, still, unless the data within the file happens to correspond to data within a pool of persistent storage. A special case is a nada byte file; these files can be newly created files that have not yet had any data written to them, or may serve every bit 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 as well a file, but as a character special file, its size is non meaningful.

Arrangement of information in a file [edit]

Information in a calculator file tin consist of smaller packets of information (oftentimes called "records" or "lines") that are individually different but share some common traits. For example, a payroll file might contain information concerning all the employees in a company and their payroll details; each record in the payroll file concerns just one employee, and all the records have the common trait of beingness related to payroll—this is very similar to placing all payroll information into a specific filing cabinet in an part that does non take a figurer. A text file may incorporate lines of text, corresponding to printed lines on a piece of paper. Alternatively, a file may contain an arbitrary binary paradigm (a blob) or information technology may contain an executable.

The way information is grouped into a file is entirely upward 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 nigh complex. Well-nigh computer files are used by computer programs which create, alter or delete the files for their own use on an as-needed footing. The programmers who create the programs determine what files are needed, how they are to be used and (often) their names.

In some cases, figurer programs dispense files that are made visible to the figurer 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 bundled in a format that the word-processing programme understands, the user is able to cull the name and location of the file and provide the bulk of the information (such as words and text) that volition be stored in the file.

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

Operations [edit]

The most basic operations that programs can perform on a file are:

• Create a new file
• Change the admission permissions and attributes of a file
• Open a file, which makes the file contents available to the programme
• Read data from a file
• Write data to a file
• Delete a file
• Close a file, terminating the association between it and the program
• Truncate a file, shortening it to a specified size within the file arrangement without rewriting any content

Files on a computer tin be created, moved, modified, grown, shrunk (truncated), and deleted. In about cases, computer programs that are executed on the computer handle these operations, merely the user of a computer can besides dispense files if necessary. For instance, Microsoft Word files are commonly created and modified past the Microsoft Word program in response to user commands, but the user can also motility, rename, or delete these files directly by using a file managing director program such as Windows Explorer (on Windows computers) or by control lines (CLI).

In Unix-like systems, user infinite programs practice 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 organisation provides a level of brainchild, which means that interaction with a file from user-space is simply through its filename (instead of its inode). For instance, rm filename will not delete the file itself, simply but a link to the file. There can be many links to a file, just when they are all removed, the kernel considers that file's retention space free to be reallocated. This free space is normally considered a security run a risk (due to the existence of file recovery software). Whatsoever secure-deletion program uses kernel-space (organisation) functions to wipe the file's data.

File moves within a file arrangement complete almost immediately because the data content does not need to exist rewritten. But the paths need to exist changed.

Moving methods [edit]

There are two singled-out implementations of file moves.

When moving files betwixt 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 in one case' only later on every file has been transferred.

With the mv command for instance, the former method is used when selecting files individually, peradventure with the use of wildcards (case: mv -n sourcePath/* targetPath, while the latter method is used when selecting entire directories (instance: mv -due north sourcePath targetPath). Microsoft Windows Explorer uses the one-time 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 afterwards the transfer has begun, pregnant after the start file is finished. With the latter method, space is simply freed after the transfer of the entire pick 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 infinite volition have been freed upward 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 private 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 (later on deletion) method will have to only delete the files from the source directory that have already finished transferring.

Identifying and organizing [edit]

Files and folders bundled in a hierarchy

In modern reckoner systems, files are typically accessed using names (filenames). In some operating systems, the name is associated with the file itself. In others, the file is bearding, and is pointed to by links that accept names. In the latter example, a user can identify the proper name of the link with the file itself, simply this is a false counterpart, especially where there exists more than one link to the same file.

Files (or links to files) can exist located in directories. Still, more generally, a directory tin can contain either a list of files or a list of links to files. Inside this definition, information technology is of paramount importance that the term "file" includes directories. This permits the existence of directory hierarchies, i.e., directories containing sub-directories. A name that refers to a file inside a directory must exist typically unique. In other words, in that location must be no identical names within a directory. However, in some operating systems, a name may include a specification of type that ways a directory can contain an identical name for more than ane type of object such as a directory and a file.

In environments in which a file is named, a file's proper name and the path to the file'south directory must uniquely place it amongst all other files in the figurer system—no two files can have the same name and path. Where a file is anonymous, named references to it volition exist within a namespace. In most cases, any name within the namespace will refer to exactly zero or 1 file. However, any file may exist represented inside whatever namespace past nix, one or more names.

Whatsoever string of characters may be a well-formed proper noun for a file or a link depending upon the context of awarding. Whether or not a name is well-formed depends on the type of computer system beingness used. Early on computers permitted only a few letters or digits in the name of a file, merely mod computers allow long names (some up to 255 characters) containing almost any combination of unicode messages or unicode digits, making information technology easier to understand the purpose of a file at a glance. Some reckoner systems allow file names to contain spaces; others practice not. Example-sensitivity of file names is determined by the file organization. Unix file systems are usually instance sensitive and let user-level applications to create files whose names differ only in the example of characters. Microsoft Windows supports multiple file systems, each with different policies^{[ which? ]} regarding instance-sensitivity. The common FAT file system tin have multiple files whose names differ only in case if the user uses a disk editor to edit the file names in the directory entries. User applications, yet, will usually non permit the user to create multiple files with the same name but differing in case.

Virtually computers organize files into hierarchies using folders, directories, or catalogs. The concept is the same irrespective of the terminology used. Each folder can comprise an arbitrary number of files, and information technology can likewise contain other folders. These other folders are referred to as subfolders. Subfolders can contain notwithstanding more files and folders and then on, thus building a tree-like structure in which one "master folder" (or "root folder" — the name varies from one operating system to another) tin contain whatsoever number of levels of other folders and files. Folders tin can be named only as files tin can (except for the root folder, which often does not have a name). The use of folders makes it easier to organize files in a logical way.

When a computer allows the use of folders, each file and folder has non only a name of its own, only likewise a path, which identifies the folder or folders in which a file or binder resides. In the path, some sort of special character—such every bit a slash—is used to divide the file and folder names. For example, in the illustration shown in this article, the path /Payroll/Salaries/Managers uniquely identifies a file called Managers in a folder called Salaries, which in turn is contained in a binder chosen Payroll. The folder and file names are separated by slashes in this example; the topmost or root binder has no name, and so the path begins with a slash (if the root folder had a proper name, it would precede this commencement slash).

Many calculator systems use extensions in file names to help identify what they incorporate, also known equally the file blazon. On Windows computers, extensions consist of a dot (period) at the end of a file proper noun, followed past a few letters to identify the type of file. An extension of .txt identifies a text file; a .doc extension identifies whatsoever type of document or documentation, commonly in the Microsoft Discussion file format; and so on. Even when extensions are used in a computer organisation, the degree to which the computer system recognizes and heeds them tin can vary; in some systems, they are required, while in other systems, they are completely ignored if they are presented.

Protection [edit]

Many modern computer systems provide methods for protecting files against adventitious and deliberate damage. Computers that allow for multiple users implement file permissions to control who may or may not alter, delete, or create files and folders. For example, a given user may be granted only permission to read a file or folder, but non to change or delete it; or a user may be given permission to read and modify files or folders, but not to execute them. Permissions may besides be used to allow but certain users to see the contents of a file or folder. Permissions protect against unauthorized tampering or destruction of information in files, and keep private information confidential from unauthorized users.

Another protection mechanism implemented in many computers is a read-only flag. When this flag is turned on for a file (which can be accomplished by a calculator program or by a man user), the file can be examined, but it cannot exist modified. This flag is useful for critical data that must not be modified or erased, such as special files that are used only by internal parts of the computer system. Some systems also include a hidden flag to make certain files invisible; this flag is used past the computer system to hide essential system files that users should not alter.

Storage [edit]

Any file that has whatever useful purpose must accept some physical manifestation. That is, a file (an abstract concept) in a real estimator system must have a existent physical counterpart if information technology is to exist at all.

In concrete terms, most computer files are stored on some blazon of data storage device. For example, most operating systems store files on a hard disk. Difficult disks have been the ubiquitous grade of non-volatile storage since the early 1960s.^[seven] Where files contain only temporary data, they may exist stored in RAM. Estimator files tin be too stored on other media in some cases, such every bit magnetic tapes, compact discs, Digital Versatile Discs, Cipher drives, USB flash drives, etc. The use of solid country drives is besides beginning to rival the hd.

In Unix-like operating systems, many files have no associated concrete storage device. Examples are /dev/null and most files under directories /dev, /proc and /sys. These are virtual files: they exist equally objects within the operating system kernel.

As seen by a running user program, files are usually represented either by a file control block or by a file handle. A file control block (FCB) is an area of memory which is manipulated to establish a filename etc. and and so passed to the operating organisation as a parameter; it was used by older IBM operating systems and early PC operating systems including CP/M and early versions of MS-DOS. A file handle is generally either an opaque data type or an integer; information technology was introduced in around 1961 by the ALGOL-based Burroughs MCP running on the Burroughs B5000 but is at present ubiquitous.

File corruption [edit]

Corrupted JPEG file, with a single bit flipped (turned from 0 to 1, or vice versa)

While there is visible corruption on the second file, one can nevertheless brand out what the original epitome might take looked similar.

When a file is said to exist corrupted, information technology is because its contents have been saved to the computer in such a way that they cannot be properly read, either by a human or by software. Depending on the extent of the damage, the original file tin sometimes be recovered, or at least partially understood.^[8] A file may be created corrupt, or it may be corrupted at a after betoken through overwriting.

There are many ways by which a file can become corrupted. Most commonly, the issue happens in the procedure of writing the file to a disk.^[9] For example, if an paradigm-editing program unexpectedly crashes while saving an image, that file may exist corrupted because the program could not save its entirety. The program itself might warn the user that there was an error, allowing for another attempt at saving the file.^[10] Some other examples of reasons for which files become corrupted include:

• The computer itself shutting downward unexpectedly (for example, due to a power loss) with open files, or files in the process of being saved;^{[eight] [9] [ten]}
• A download being interrupted before it was completed;
• Due to a bad sector on the hard bulldoze;^{[8] [9]}
• The user removing a wink drive (such as a USB stick) without properly unmounting (usually referred to as "safely removing");^{[11] [12] [13] [xiv]}
• Malicious software, such every bit a computer virus;^{[8] [ix] [15] [16]}
• A wink drive becoming also old.^[14]

Although file corruption usually happens accidentally, it may also be washed on purpose, as to fool someone else into thinking an assignment was gear up at an earlier date, potentially gaining time to finish said assignment. There are services that provide on demand file corruption, which essentially fill up a given file with random data so that it cannot be opened or read, yet still seems legitimate.^{[17] [eighteen]}

One of the most constructive countermeasures for unintentional file corruption is backing up important files.^[nineteen] In the event of an important file becoming corrupted, the user can simply replace it with the backed up version.

Backup [edit]

When computer files contain information that is extremely important, a back-up process is used to protect confronting disasters that might destroy the files. Backing up files simply means making copies of the files in a separate location so that they can exist restored if something happens to the computer, or if they are deleted accidentally.

At that place are many ways to back up files. About calculator systems provide utility programs to assist in the dorsum-upwards process, which can become very time-consuming if there are many files to safeguard. Files are frequently copied to removable media such every bit writable CDs or cartridge tapes. Copying files to another hard disk in the aforementioned computer protects against failure of one disk, just if it is necessary to protect against failure or destruction of the unabridged computer, so copies of the files must be made on other media that tin be taken away from the computer and stored in a safe, distant location.

The grandfather-father-son backup method automatically makes iii back-ups; the granddaddy file is the oldest copy of the file and the son is the current copy.

File systems and file managers [edit]

The way a reckoner organizes, names, stores and manipulates files is globally referred to every bit its file system. Most computers accept at least 1 file system. Some computers allow the use of several different file systems. For instance, on newer MS Windows computers, the older FAT-type file systems of MS-DOS and onetime versions of Windows are supported, in addition to the NTFS file system that is the normal file arrangement for contempo versions of Windows. Each system has its own advantages and disadvantages. Standard FAT allows only 8-grapheme file names (plus a iii-grapheme extension) with no spaces, for example, whereas NTFS allows much longer names that can comprise spaces. You can call a file "Payroll records" in NTFS, but in Fatty you would be restricted to something like payroll.dat (unless you were using VFAT, a FAT extension allowing long file names).

File manager programs are utility programs that allow users to manipulate files straight. They allow you to motion, create, delete and rename files and folders, although they practise not actually allow you to read the contents of a file or store data in it. Every computer organization provides at to the lowest degree one file-manager program for its native file system. For instance, File Explorer (formerly Windows Explorer) is unremarkably used in Microsoft Windows operating systems, and Nautilus is common under several distributions of Linux.

See also [edit]

• Block (information storage)
• Calculator file management
• Data hierarchy
• File camouflage
• File copying
• File conversion
• File deletion
• File directory
• File manager
• File arrangement
• Filename
• Apartment-file database
• Object composition
• Soft copy

References [edit]

1. ^ "Online Etymology Dictionary".
2. ^ Eckert, W. J.; Thomas J. Watson Astronomical Computing Agency, New York. (1940). Punched card methods in scientific computation. New York: The Thomas J. Watson Astronomical Calculating Bureau, Columbia University.
3. ^ Comrie, L. J. (1928-04-13). "On the Construction of Tables by Interpolation (Plate 6)". Monthly Notices of the Purple Astronomical Society. 88 (six): 506–523. Bibcode:1928MNRAS..88..506C. doi:10.1093/mnras/88.half-dozen.506. ISSN 0035-8711.
4. ^ Popular Science. Bonnier Corporation. February 1950. p. 96. Retrieved 2014-03-07 .
5. ^ Robert South. Casey, et al. Punched Cards: Their Applications to Scientific discipline and Manufacture. 1952.
6. ^ Martin H. Weik. Ballistic Research Laboratories Study #1115. March 1961. pp. 314–331.
7. ^ Magnetic Storage Handbook 2nd Ed., Section 2.1.1, Deejay File Engineering, Mee and Daniel, (c)1990,
8. ^ ^{a b c d} Gorski, Victoria. "What Causes a Corrupt File?". Retrieved 2019-03-17 .
9. ^ ^{a b c d} Williams, Jane (2019-01-14). "What Does Information technology Hateful When Your File Is Corrupt?". Houston Chronicle . Retrieved 2019-03-17 .
10. ^ ^{a b} Glenn, Walter (2017-12-fourteen). "What Is a Corrupted File, and Is There a Way to Get Information technology Dorsum?". How-To Geek. Archived from the original on 2018-12-06. Retrieved 2019-03-17 .
11. ^ "What Causes Flash Retentiveness Abuse?". SecureDataRecovery. Retrieved 2019-03-17 .
12. ^ Hoffman, Chris (2016-09-28). "Do You Really Need to Safely Remove USB Flash Drives?". How-To Geek. Retrieved 2019-03-17 .
13. ^ "Open a certificate after a file abuse error". Microsoft Role Support. Retrieved 2019-03-17 .
14. ^ ^{a b} "What kills your Wink Bulldoze and how y'all tin can avoid information technology". DataRecovery.net. Retrieved 2019-03-17 .
15. ^ Neagoe, Robert (2018-08-14). "Fix Windows 10 File Corruption Problems". Windowsreport.com. Retrieved 2019-03-17 .
16. ^ International Quango of Electronic Commerce Consultants (2009-09-24). "Mac Os Ten Hacking". Ethical Hacking and Countermeasures: Linux, Macintosh and Mobile Systems. Cengage. pp. 2.6–2.vii. ISBN978-1-4354-8364-four . Retrieved 2019-03-17 .
17. ^ "Decadent a file - Corrupt file online, deliver on time!". Retrieved 2019-03-17 .
18. ^ "Decadent My File: Get your file corrupted for y'all". Retrieved 2019-03-17 .
19. ^ "What is a Corrupted File?". Intego. 2019-03-07.

External links [edit]

• Media related to Reckoner files at Wikimedia Commons
• Data Formats Computer file at Curlie

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Source: https://en.wikipedia.org/wiki/Computer_file

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