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File Comparison
In computing, file comparison is the calculation and display of the differences and similarities between data objects, typically text files such as source code. The methods, implementations, and results are typically called a diff, after the Unix diff utility. The output may be presented in a graphical user interface or used as part of larger tasks in networks, file systems, or revision control. Some widely used file comparison programs are diff, cmp, FileMerge, WinMerge, Beyond Compare, and File Compare. Many text editors and word processors perform file comparison to highlight the changes to a file or document. Method types Most file comparison tools find the longest common subsequence between two files. Any data not in the longest common subsequence is presented as a change or an insertion or a deletion. In 1978, Paul Heckel published an algorithm that identifies most moved blocks of text. This is used in the IBM History Flow tool. Other file comparison programs ...
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Word Processor
A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features. Early word processors were stand-alone devices dedicated to the function, but current word processors are word processor programs running on general purpose computers. The functions of a word processor program fall somewhere between those of a simple text editor and a fully functioned desktop publishing program. However, the distinctions between these three have changed over time and were unclear after 2010. Background Word processors did not develop ''out'' of computer technology. Rather, they evolved from mechanical machines and only later did they merge with the computer field. The history of word processing is the story of the gradual automation of the physical aspects of writing and editing, and then to the refinement of the technology to make it available to corporations and Individuals. The term ''word proces ...
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Punched Card
A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to directly control automated machinery. Punched cards were widely used through much of the 20th century in the data processing industry, where specialized and increasingly complex unit record machines, organized into semiautomatic data processing systems, used punched cards for data input, output, and storage. The IBM 12-row/80-column punched card format came to dominate the industry. Many early digital computers used punched cards as the primary medium for input of both computer programs and data. While punched cards are now obsolete as a storage medium, as of 2012, some voting machines still used punched cards to record votes. They also had a significant cultural impact. History The idea of control and data storage via punched hole ...
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IBM 519
The IBM 519 Document-Originating Machine, introduced in 1946, was the last in a series of unit record machines designed for automated preparation of punched cards. Others in the series included the IBM 513 & IBM 514 Reproducing Punch. The 519, which was "state of the art for the time", could: * reproduce all or parts of the information on a set of cards * " gangpunch" - copy information from a master card into the following detail cards * print up to eight digits on the end of a card * compare two decks of cards * "summary punch" — create punch cards containing summary information provided by a connected accounting machine, such as totals from a group of processed cards * "mark sense" — detect marks made with an electrographic pencil in designated locations on a punched card and then punch holes corresponding to those marks into the card * number cards consecutively (an optional feature) The reproducing, gangpunching, summary punching, and comparing features of the IBM 519 are ...
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Data Corruption
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted. A datum is an individual value in a collection of data. Data is usually organized into structures such as tables that provide additional context and meaning, and which may themselves be used as data in larger structures. Data may be used as variables in a computational process. Data may represent abstract ideas or concrete measurements. Data is commonly used in scientific research, economics, and in virtually every other form of human organizational activity. Examples of data sets include price indices (such as consumer price index), unemployment rates, literacy rates, and census data. In this context, data represents the raw facts and figures which can be used in such a manner in order to capture the useful information out of it. ...
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Backup
In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "back up", whereas the noun and adjective form is "backup". Backups can be used to recover data after its loss from data deletion or corruption, or to recover data from an earlier time. Backups provide a simple form of disaster recovery; however not all backup systems are able to reconstitute a computer system or other complex configuration such as a computer cluster, active directory server, or database server. A backup system contains at least one copy of all data considered worth saving. The data storage requirements can be large. An information repository model may be used to provide structure to this storage. There are different types of data storage devices used for copying backups of data that is already in secondary storage onto archive ...
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File Synchronization
File synchronization (or syncing) in computing is the process of ensuring that computer files in two or more locations are updated via certain rules. In ''one-way file synchronization'', also called mirroring, updated files are copied from a source location to one or more target locations, but no files are copied back to the source location. In ''two-way file synchronization'', updated files are copied in both directions, usually with the purpose of keeping the two locations identical to each other. In this article, the term synchronization refers exclusively to two-way file synchronization. File synchronization is commonly used for home backups on external hard drives or updating for transport on USB flash drives. BitTorrent Sync, Dropbox and SKYSITE are prominent products. Some backup software also support real-time file sync. The automatic process prevents copying already identical files and thus can be faster and save much time versus a manual copy, and is less error prone. ...
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Computer Program
A computer program is a sequence or set of instructions in a programming language for a computer to Execution (computing), execute. Computer programs are one component of software, which also includes software documentation, documentation and other intangible components. A computer program in its human-readable form is called source code. Source code needs another computer program to Execution (computing), execute because computers can only execute their native machine code, machine instructions. Therefore, source code may be translated to machine instructions using the language's compiler. (Assembly language programs are translated using an Assembly language#Assembler, assembler.) The resulting file is called an executable. Alternatively, source code may execute within the language's interpreter (computing), interpreter. If the executable is requested for execution, then the operating system Loader (computing), loads it into Random-access memory, memory and starts a Process (com ...
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Folding Editor
Code or text folding, or less commonly holophrasting, is a feature of some graphical user interfaces that allows the user to selectively hide ("fold") or display ("unfold") parts of a document. This allows the user to manage large amounts of text while viewing only those subsections that are currently of interest. It is typically used with documents which have a natural tree structure consisting of nested elements. Other names for these features include expand and collapse, code hiding, and outlining. In Microsoft Word, the feature is called "collapsible outlining". Many user interfaces provide disclosure widgets for code folding in a sidebar, indicated for example by a triangle that points sideways (if collapsed) or down (if expanded), or by a /code> box for collapsible (expanded) text, and a /code> box for expandable (collapsed) text. Code folding is found in text editors, source code editors, and IDEs. The folding structure typically follows the syntax tree of the pro ...
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Code Folding
Code or text folding, or less commonly holophrasting, is a feature of some graphical user interfaces that allows the user to selectively hide ("fold") or display ("unfold") parts of a document. This allows the user to manage large amounts of text while viewing only those subsections that are currently of interest. It is typically used with documents which have a natural tree structure consisting of nested elements. Other names for these features include expand and collapse, code hiding, and outlining. In Microsoft Word, the feature is called "collapsible outlining". Many user interfaces provide disclosure widgets for code folding in a sidebar, indicated for example by a triangle that points sideways (if collapsed) or down (if expanded), or by a /code> box for collapsible (expanded) text, and a /code> box for expandable (collapsed) text. Code folding is found in text editors, source code editors, and IDEs. The folding structure typically follows the syntax tree of the progr ...
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Rolling Hash
A rolling hash (also known as recursive hashing or rolling checksum) is a hash function where the input is hashed in a window that moves through the input. A few hash functions allow a rolling hash to be computed very quickly—the new hash value is rapidly calculated given only the old hash value, the old value removed from the window, and the new value added to the window—similar to the way a moving average function can be computed much more quickly than other low-pass filters. One of the main applications is the Rabin–Karp string search algorithm, which uses the rolling hash described below. Another popular application is the rsync program, which uses a checksum based on Mark Adler's adler-32 as its rolling hash. Low Bandwidth Network Filesystem (LBFS) uses a Rabin fingerprint as its rolling hash. FastCDC (Fast Content-Defined Chunking) uses a compute-efficient Gear fingerprint as its rolling hash. At best, rolling hash values are pairwise independentDaniel Lemire, Owen ...
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Rsync
rsync is a utility for efficiently transferring and synchronizing files between a computer and a storage drive and across networked computers by comparing the modification times and sizes of files. It is commonly found on Unix-like operating systems and is under the GPL-3.0-or-later license. Rsync is written in C as a single threaded application. The rsync algorithm is a type of delta encoding, and is used for minimizing network usage. Zlib may be used for additional data compression, and SSH or stunnel can be used for security. Rsync is typically used for synchronizing files and directories between two different systems. For example, if the command rsync local-file user@remote-host:remote-file is run, rsync will use SSH to connect as user to remote-host. Once connected, it will invoke the remote host's rsync and then the two programs will determine what parts of the local file need to be transferred so that the remote file matches the local one. One application of ...
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