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Varicode
Varicode is a self-synchronizing code for use in PSK31. It supports all ASCII characters, but the characters used most frequently in English have shorter codes. The space between characters is indicated by a 00 sequence, an implementation of Fibonacci coding. Originally created for speeding up real-time keyboard-to-keyboard exchanges over low bandwidth links, Varicode is freely available. Limitations * Varicode provides somewhat weaker compression in languages other than English that use same characters as in English. Varicode table Control characters Printable characters Character lengths Beginning with the single-bit code "1", valid varicode values may be formed by prefixing a "1" or "10" to a shorter code. Thus, the number of codes of length ''n'' is equal to the Fibonacci number In mathematics, the Fibonacci sequence is a Integer sequence, sequence in which each element is the sum of the two elements that precede it. Numbers that are part of the Fibonacci sequence ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PSK31
PSK31 or "Phase-shift keying, Phase Shift Keying, 31 Baud", also BPSK31 and QPSK31, is a popular computer-sound card-generated radioteletype mode, used primarily by amateur radio operators to conduct real-time keyboard-to-keyboard Synchronous conferencing, chat, most often using frequencies in the high frequency amateur radio bands (shortwave). PSK31 is distinguished from other digital modes in that it is specifically tuned to have a data rate close to typing speed, and has an extremely narrow bandwidth, allowing many conversations in the same bandwidth as a single voice channel. This narrow bandwidth (signal processing), bandwidth makes better use of the Radio frequency, RF energy in a very narrow space thus allowing relatively low-power equipment (5 watts) to communicate globally using the same skywave radio propagation, propagation used by shortwave listening, shortwave radio stations. History PSK31 was developed and named by English amateur radio operator Peter Martinez (A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fibonacci Coding
In mathematics and computing, Fibonacci coding is a universal code which encodes positive integers into binary code words. It is one example of representations of integers based on Fibonacci numbers. Each code word ends with "11" and contains no other instances of "11" before the end. The Fibonacci code is closely related to the Zeckendorf representation, a positional numeral system that uses Zeckendorf's theorem and has the property that no number has a representation with consecutive 1s. The Fibonacci code word for a particular integer is exactly the integer's Zeckendorf representation with the order of its digits reversed and an additional "1" appended to the end. Definition For a number N\!, if d(0),d(1),\ldots,d(k-1),d(k)\! represent the digits of the code word representing N\! then we have: : N = \sum_^ d(i) F(i+2),\textd(k-1)=d(k)=1.\! where is the th Fibonacci number, and so is the th distinct Fibonacci number starting with 1,2,3,5,8,13,\ldots. The last bit d(k) i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-synchronizing Code
In coding theory, especially in telecommunications, a self-synchronizing code is a uniquely decodable code in which the symbol stream formed by a portion of one code word, or by the overlapped portion of any two adjacent code words, is not a valid code word. Put another way, a set of strings (called "code words") over an alphabet is called a self-synchronizing code if for each string obtained by concatenating two code words, the substring starting at the second symbol and ending at the second-last symbol does not contain any code word as substring. Every self-synchronizing code is a prefix code, but not all prefix codes are self-synchronizing. Other terms for self-synchronizing code are synchronized code or, ambiguously, comma-free code. A self-synchronizing code permits the proper framing of transmitted code words provided that no uncorrected errors occur in the symbol stream; external synchronization is not required. Self-synchronizing codes also allow recovery from uncor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bracket
A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. They come in four main pairs of shapes, as given in the box to the right, which also gives their names, that vary between British and American English. "Brackets", without further qualification, are in British English the ... marks and in American English the ... marks. Other symbols are repurposed as brackets in specialist contexts, such as those used by linguists. Brackets are typically deployed in symmetric pairs, and an individual bracket may be identified as a "left" or "right" bracket or, alternatively, an "opening bracket" or "closing bracket", respectively, depending on the directionality of the context. In casual writing and in technical fields such as computing or linguistic analysis of grammar, brackets nest, with segments of bracketed material containing embedded within them other further bracketed sub-segments. The nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apostrophe (punctuation)
The apostrophe (, ) is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet and some other alphabets. In English, the apostrophe is used for two basic purposes: * The marking of the omission of one or more letters, e.g. the contraction of "do not" to "don't" * The marking of possessive case of nouns (as in "the eagle's feathers", "in one month's time", "the twins' coats") It is also used in a few exceptional cases for the marking of plurals, e.g. "p's and q's" or Oakland A's. The same mark is used as a single quotation mark. It is also substituted informally for other marks for example instead of the prime symbol to indicate the units of foot or minutes of arc. The word ''apostrophe'' comes from the Greek (hē apóstrophos rosōidía ' he accent ofturning away or elision'), through Latin and French. Usage in English Historical development The apostrophe was first used by Pietro Bembo in his edition of '' De Aetna'' (1496). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ampersand
The ampersand, also known as the and sign, is the logogram , representing the grammatical conjunction, conjunction "and". It originated as a typographic ligature, ligature of the letters of the word (Latin for "and"). Etymology Traditionally in English, when spelling aloud, any letter that could also be used as a word in itself ("A", "I", and "Vocative case#English, O") was referred to by the Latin expression ('by itself'), as in "''per se'' A" or "A ''per se'' A". The character &, when used by itself as opposed to more extended forms such as ''&c.'', was similarly referred to as "and ''per se'' and". This last phrase was routinely slurred to "ampersand", and the term had entered common English usage by 1837. It has been false etymology, falsely claimed that André-Marie Ampère used the symbol in his widely read publications and that people began calling the new shape "Ampère's and". History The ampersand can be traced back to the 1st century AD and the old Roma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Percent Sign
The percent sign (sometimes per cent sign in British English) is the symbol used to indicate a percentage, a number or ratio as a fraction (mathematics), fraction of 100. Related signs include the permille (per thousand) sign and the Basis point#Permyriad, permyriad (per ten thousand) sign (also known as a basis point), which indicate that a number is divided by one thousand or ten thousand, respectively. Higher proportions use parts-per notation. Correct style Form and spacing English style guides prescribe writing the percent sign following the number without any space between (e.g. 50%). However, the International System of Units and ISO 31-0 standard prescribe a space between the number and percent sign, in line with the general practice of using a non-breaking space between a numerical value and its corresponding unit of measurement. Other languages have other rules for spacing in front of the percent sign: * In Czech language, Czech and in Slovak language, S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dollar Sign
The dollar sign, also known as the peso sign, is a currency symbol consisting of a Letter case, capital crossed with one or two vertical strokes ( or depending on typeface), used to indicate the unit of various currency, currencies around the world, including most currencies denominated "dollar" or "peso". The explicitly double-barred sign is called cifrão in the Portuguese language. The sign is also used in several compound currency symbols, such as the Brazilian real (R$) and the United States dollar (US$): in local use, the nationality prefix is usually omitted. In countries that have other currency symbols, the US dollar is often assumed and the "US" prefix omitted. The one- and two-stroke versions are often considered mere stylistic (typeface) variants, although in some places and epochs one of them may have been specifically assigned, by law or custom, to a specific currency. The Unicode computer encoding standard defines a single code for both. In most English l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Number Sign
The symbol is known as the number sign, hash, (or in North America) the pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a Typographic ligature, ligatured abbreviation for Pound (mass), pounds avoirdupois – having been derived from the now-rare . Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as "hashtags", and from that, the symbol itself is sometimes called a hashtag. The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes. History It is believed that the symbol traces its origins to the symbol , an abbreviation of the Roman term ''Roman pound, libra pondo'', which translates as "pound weight". The abbreviation "lb" was printed as a dedicated Ligature (writing), ligature including a horizontal line across (which indicated abbreviation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quotation Mark
Quotation marks are punctuation marks used in pairs in various writing systems to identify direct speech, a quotation, or a phrase. The pair consists of an opening quotation mark and a closing quotation mark, which may or may not be the same glyph. Quotation marks have a variety of forms in different languages and in different media. History The single quotation mark is traced to Ancient Greek practice, adopted and adapted by monastic copyists. Isidore of Seville, in his seventh century encyclopedia, , described their use of the Greek ''diplé'' (a Angle bracket, chevron): The double quotation mark derives from a marginal notation used in fifteenth-century manuscript annotations to indicate a passage of particular importance (not necessarily a quotation); the notation was placed in the outside margin of the page and was repeated alongside each line of the passage. In his edition of the works of Aristotle, which appeared in 1483 or 1484, the Milanese Renaissance humanis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exclamation Mark
The exclamation mark (also known as exclamation point in American English) is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or to show wikt:emphasis, emphasis. The exclamation mark often marks the end of a sentence, for example: "Watch out!". Similarly, a bare exclamation mark (with nothing before or after) is frequently used in warning signs. Additionally, the exclamation mark is commonly used in writing to make a character seem as though they are shouting, excited, or surprised. Other uses include: * In mathematics, it denotes the factorial operation. * Several computer languages use at the beginning of an expression (computer science), expression to denote logical negation. For example, means "the logical negation of A", also called "not A". This usage has spread to ordinary language (e.g., "!clue" means no-clue or clueless). * Some languages use ǃ, a symbol that looks like an exclamation mark, to denote a click consonant. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space (punctuation)
In writing, a space () is a blank area that word divider, separates words, Sentence spacing, sentences, and other written or printed glyphs (characters). Conventions for spacing vary among languages, and in some languages the spacing rules are complex. Inter-word spaces ease the reader's task of identifying words, and avoid outright ambiguities such as "now here" vs. "nowhere". They also provide convenient guides for where a human or program may start new lines. Typesetting can use spaces of varying widths, just as it can use graphic characters of varying widths. Unlike graphic characters, typeset spaces are Typographic alignment, commonly stretched in order to align text. A typewriter, on the other hand, typically has only one width for all characters, including spaces. Following widespread acceptance of the typewriter, some typewriter conventions influenced typography and the design of printed works. Computer representation of text facilitates getting around mechanical and phys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
