In computer science, the Boolean satisfiability problem is the problem of determining if there exists an interpretation that satisfies a given Boolean formula. In other words, it asks whether the variables of a given Boolean formula can be consistently replaced by the values TRUE or FALSE in such a way that the formula evaluates to TRUE. If this is the case, the formula is called satisfiable. On the other hand, if no such assignment exists, the function expressed by the formula is FALSE for all possible variable assignments and the formula is unsatisfiable. For example, the formula "a AND NOT b" is satisfiable because one can find the values a = TRUE and b = FALSE, which make = TRUE. In contrast, "a AND NOT a" is unsatisfiable.
Bi-directional text is text containing text in both text directionalities, both right-to-left and left-to-right. It generally involves text containing different types of alphabets, but may also refer to boustrophedon, which is changing text directionality in each row.
In signal processing, data compression, source coding, or bit-rate reduction involves encoding information using fewer bits than the original representation. Compression can be either lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy. No information is lost in lossless compression. Lossy compression reduces bits by removing unnecessary or less important information.
gzip is a file format and a software application used for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU. Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993.
Lossless compression is a class of data compression algorithms that allows the original data to be perfectly reconstructed from the compressed data. By contrast, lossy compression permits reconstruction only of an approximation of the original data, though usually with improved compression rates.
Run-length encoding (RLE) is a very simple form of lossless data compression in which runs of data are stored as a single data value and count, rather than as the original run. This is most useful on data that contains many such runs. Consider, for example, simple graphic images such as icons, line drawings, Conway’s Game of Life, and animations. It is not useful with files that don't have many runs as it could greatly increase the file size.
In computing, Deflate is a lossless data compression algorithm and associated file format that uses a combination of the LZ77 algorithm and Huffman coding. It was originally defined by Phil Katz for version 2 of his PKZIP archiving tool. The file format was later specified in RFC 1951.
In computing, the diff utility is a data comparison tool that calculates and displays the differences between two files. Unlike edit distance notions used for other purposes, diff is line-oriented rather than character-oriented, but it is like Levenshtein distance in that it tries to determine the smallest set of deletions and insertions to create one file from the other. The diff command displays the changes made in a standard format, such that both humans and machines can understand the changes and apply them: given one file and the changes, the other file can be created.
ISO/IEC 7810 Identification cards — Physical characteristics is an international standard that defines the physical characteristics for identification cards.
In numerical analysis and computer science, a sparse matrix or sparse array is a matrix in which most of the elements are zero. By contrast, if most of the elements are nonzero, then the matrix is considered dense. The number of zero-valued elements divided by the total number of elements is called the sparsity of the matrix. Using those definitions, a matrix will be sparse when its sparsity is greater than 0.5.
True Audio (TTA) is a lossless compressor for multichannel 8, 16 and 24 bits audio data.
.tta is the extension to filenames of audio files created by the True Audio codec.
The International Standard Music Number or ISMN is a thirteen-character alphanumeric identifier for printed music developed by ISO.
Image file formats are standardized means of organizing and storing digital images. Image files are composed of digital data in one of these formats that can be rasterized for use on a computer display or printer. An image file format may store data in uncompressed, compressed, or vector formats. Once rasterized, an image becomes a grid of pixels, each of which has a number of bits to designate its color equal to the color depth of the device displaying it.
A tag editor is a piece of software that supports editing metadata of multimedia file formats, rather than the actual file content. These are mainly taggers for common audio tagging formats like ID3, APE, and Vorbis comments, but can also be taggers for JPEG, PDF and TIFF metadata.
Constrained Energy Lapped Transform (CELT) is an open, royalty-free lossy audio compression format and a free software codec with especially low algorithmic delay for use in low-latency audio communication. The algorithms are openly documented and may be used free of software patent restrictions. Development of the format was maintained by the Xiph.Org Foundation and later coordinated by the Opus working group of the Internet Engineering Task Force (IETF).
ssh-keygen is a standard component of the Secure Shell (SSH) protocol suite found on Unix and Unix-like computer systems used to establish secure shell sessions between remote computers over insecure networks, through the use of various cryptographic techniques. The ssh-keygen utility is used to generate, manage, and convert authentication keys.
ISO 9564 is an international standard for personal identification number (PIN) management and security in financial services.
In computer programming, string interpolation is the process of evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values. It is a form of simple template processing or, in formal terms, a form of quasi-quotation. String interpolation allows easier and more intuitive string formatting and content-specification compared with string concatenation.
In cryptography and computer security, a length extension attack is a type of attack where an attacker can use Hash(message1) and the length of message1 to calculate Hash(message1 ‖ message2) for an attacker-controlled message2, without needing to know the content of message1. Algorithms like MD5, SHA-1, and SHA-2 that are based on the Merkle–Damgård construction are susceptible to this kind of attack. The SHA-3 algorithm is not susceptible.
crypt is the library function which is used to compute a password hash that can be used to store user account passwords while keeping them relatively secure. The output of the function is not simply the hash – it is a text string which also encodes the salt, and identifies the hash algorithm used. This output string is what is meant for putting in a password record which may be stored in a plain text file.
