Topic: computing (Page 13)
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๐ Pentium floating-point division bug (1994)
The Pentium FDIV bug is a hardware bug affecting the floating-point unit (FPU) of the early Intel Pentium processors. Because of the bug, the processor would return incorrect binary floating point results when dividing certain pairs of high-precision numbers. The bug was discovered in 1994 by Thomas R. Nicely, a professor of mathematics at Lynchburg College. Missing values in a lookup table used by the FPU's floating-point division algorithm led to calculations acquiring small errors. While these errors would in most use-cases only occur rarely and result in small deviations from the correct output values, in certain circumstances the errors can occur frequently and lead to more significant deviations.
The severity of the FDIV bug is debated. Though rarely encountered by most users (Byte magazine estimated that 1 in 9 billion floating point divides with random parameters would produce inaccurate results), both the flaw and Intel's initial handling of the matter were heavily criticized by the tech community.
In December 1994, Intel recalled the defective processors in what was the first full recall of a computer chip. In its 1994 annual report, Intel said it incurred "a $475 million pre-tax chargeย ... to recover replacement and write-off of these microprocessors."
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- "Pentium floating-point division bug (1994)" | 2023-08-09 | 111 Upvotes 62 Comments
๐ CueCat
The CueCat, styled :CueCat with a leading colon, is a cat-shaped handheld barcode reader that was given away free to Internet users starting in 2000 by the now-defunct Digital Convergence Corporation. The CueCat was named CUE for the unique bar code which the device scanned and CAT as a play on "Keystroke Automation Technology" and it enabled a user to open a link to an Internet URL by scanning a barcode โ called a "cue" by Digital Convergence โ appearing in an article or catalog or on some other printed matter. In this way, a user could be directed to a web page containing related information without having to enter a URL. The company asserted that the ability of the device to direct users to a specific URL, rather than a domain name, was valuable. In addition, television broadcasters could use an audio tone in programs or commercials that, if a TV was connected to a computer via an audio cable, acted as a web address shortcut.
The CueCat connected to computers using the PS/2 keyboard port and USB, and communicated to desktop "CRQ" software running on Windows 32-bit and Mac OS 9 operating systems. Users of this software were required to register with their ZIP code, gender, and email address. This registration process enabled the device to deliver relevant content to a single or multiple users in a household.
By year-end 2001, Codes could no longer be generated for the device or scanned with the device. However, third-party software can decode the lightweight encryption in the device.
๐ Flashsort
Flashsort is a distribution sorting algorithm showing linear computational complexity for uniformly distributed data sets and relatively little additional memory requirement. The original work was published in 1998 by Karl-Dietrich Neubert.
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- "Flashsort" | 2020-02-09 | 141 Upvotes 31 Comments
๐ Logic Theorist
Logic Theorist is a computer program written in 1956 by Allen Newell, Herbert A. Simon and Cliff Shaw. It was the first program deliberately engineered to perform automated reasoning and is called "the first artificial intelligence program". It would eventually prove 38 of the first 52 theorems in Whitehead and Russell's Principia Mathematica, and find new and more elegant proofs for some.
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- "Logic Theorist" | 2018-07-06 | 128 Upvotes 33 Comments
๐ Nomogram
A nomogram (from Greek ฮฝฯฮผฮฟฯ nomos, "law" and ฮณฯฮฑฮผฮผฮฎ grammฤ, "line"), also called a nomograph, alignment chart, or abaque, is a graphical calculating device, a two-dimensional diagram designed to allow the approximate graphical computation of a mathematical function. The field of nomography was invented in 1884 by the French engineer Philbert Maurice d'Ocagne (1862โ1938) and used extensively for many years to provide engineers with fast graphical calculations of complicated formulas to a practical precision. Nomograms use a parallel coordinate system invented by d'Ocagne rather than standard Cartesian coordinates.
A nomogram consists of a set of n scales, one for each variable in an equation. Knowing the values of n-1 variables, the value of the unknown variable can be found, or by fixing the values of some variables, the relationship between the unfixed ones can be studied. The result is obtained by laying a straightedge across the known values on the scales and reading the unknown value from where it crosses the scale for that variable. The virtual or drawn line created by the straightedge is called an index line or isopleth.
Nomograms flourished in many different contexts for roughly 75 years because they allowed quick and accurate computations before the age of pocket calculators. Results from a nomogram are obtained very quickly and reliably by simply drawing one or more lines. The user does not have to know how to solve algebraic equations, look up data in tables, use a slide rule, or substitute numbers into equations to obtain results. The user does not even need to know the underlying equation the nomogram represents. In addition, nomograms naturally incorporate implicit or explicit domain knowledge into their design. For example, to create larger nomograms for greater accuracy the nomographer usually includes only scale ranges that are reasonable and of interest to the problem. Many nomograms include other useful markings such as reference labels and colored regions. All of these provide useful guideposts to the user.
Like a slide rule, a nomogram is a graphical analog computation device, and like the slide rule, its accuracy is limited by the precision with which physical markings can be drawn, reproduced, viewed, and aligned. While the slide rule is intended to be a general-purpose device, a nomogram is designed to perform a specific calculation, with tables of values effectively built into the construction of the scales. Nomograms are typically used in applications where the level of accuracy they offer is sufficient and useful. Alternatively, a nomogram can be used to check an answer obtained from another, more exact but possibly error-prone calculation.
Other types of graphical calculators such as intercept charts, trilinear diagrams and hexagonal charts are sometimes called nomograms. Other such examples include the Smith chart, a graphical calculator used in electronics and systems analysis, thermodynamic diagrams and tephigrams, used to plot the vertical structure of the atmosphere and perform calculations on its stability and humidity content. These do not meet the strict definition of a nomogram as a graphical calculator whose solution is found by the use of one or more linear isopleths.
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- "Nomogram" | 2023-12-15 | 12 Upvotes 1 Comments
- "Nomogram" | 2019-11-26 | 90 Upvotes 8 Comments
- "Nomogram" | 2014-08-31 | 50 Upvotes 7 Comments
๐ COMEFROM
In computer programming, COMEFROM (or COME FROM) is an obscure control flow structure used in some programming languages, originally as a joke. COMEFROM is roughly the opposite of GOTO in that it can take the execution state from any arbitrary point in code to a COMEFROM statement.
The point in code where the state transfer happens is usually given as a parameter to COMEFROM. Whether the transfer happens before or after the instruction at the specified transfer point depends on the language used. Depending on the language used, multiple COMEFROMs referencing the same departure point may be invalid, be non-deterministic, be executed in some sort of defined priority, or even induce parallel or otherwise concurrent execution as seen in Threaded Intercal.
A simple example of a "COMEFROM x" statement is a label x (which does not need to be physically located anywhere near its corresponding COMEFROM) that acts as a "trap door". When code execution reaches the label, control gets passed to the statement following the COMEFROM. This may also be conditional, passing control only if a condition is satisfied, analogous to a GOTO within an IF statement. The primary difference from GOTO is that GOTO only depends on the local structure of the code, while COMEFROM depends on the global structure โ a GOTO transfers control when it reaches a line with a GOTO statement, while COMEFROM requires scanning the entire program or scope to see if any COMEFROM statements are in scope for the line, and then verifying if a condition is hit. The effect of this is primarily to make debugging (and understanding the control flow of the program) extremely difficult, since there is no indication near the line or label in question that control will mysteriously jump to another point of the program โ one must study the entire program to see if any COMEFROM statements reference that line or label.
Debugger hooks can be used to implement a COMEFROM statement, as in the humorous Python goto module; see below. This also can be implemented with the gcc feature "asm goto" as used by the Linux kernel configuration option CONFIG_JUMP_LABEL. A no-op has its location stored, to be replaced by a jump to an executable fragment that at its end returns to the instruction after the no-op.
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- "COMEFROM" | 2019-10-19 | 82 Upvotes 24 Comments
- "COMEFROM" | 2011-11-17 | 41 Upvotes 20 Comments
๐ Cool stuff you can do with netcat
netcat (often abbreviated to nc) is a computer networking utility for reading from and writing to network connections using TCP or UDP. The command is designed to be a dependable back-end that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging and investigation tool, since it can produce almost any kind of connection its user could need and has a number of built-in capabilities.
Its list of features includes port scanning, transferring files, and port listening, and it can be used as a backdoor.
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- "Cool stuff you can do with netcat" | 2010-11-05 | 126 Upvotes 39 Comments
๐ Stanford Bunny
The Stanford bunny is a computer graphics 3D test model developed by Greg Turk and Marc Levoy in 1994 at Stanford University. The model consists of 69,451 triangles, with the data determined by 3D scanning a ceramic figurine of a rabbit. This figurine and others were scanned to test methods of range scanning physical objects.
The data can be used to test various graphics algorithms, including polygonal simplification, compression, and surface smoothing. There are a few complications with this dataset that can occur in any 3D scan data: the model is manifold connected and has holes in the data, some due to scanning limits and some due to the object being hollow. These complications provide a more realistic input for any algorithm that is benchmarked with the Stanford bunny, though by today's standards, in terms of geometric complexity and triangle count, it is considered a simple model.
The model was originally available in .ply (polygons) file format with 4 different resolutions.
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- "Stanford Bunny" | 2021-05-25 | 121 Upvotes 42 Comments
๐ The Amiga Smart File System
The Smart File System (SFS) is a journaling filesystem used on Amiga computers and AmigaOS-derived operating systems (though some support also exists for IBM PC compatibles). It is designed for performance, scalability and integrity, offering improvements over standard Amiga filesystems as well as some special or unique features.
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- "The Amiga Smart File System" | 2019-09-01 | 129 Upvotes 32 Comments
๐ NeWS โ Network Extensible Window System
NeWS (Network extensible Window System) is a discontinued windowing system developed by Sun Microsystems in the mid-1980s. Originally known as "SunDew", its primary authors were James Gosling and David S. H. Rosenthal. The NeWS interpreter was based on PostScript (as was the later Display PostScript, although the two projects were otherwise unrelated) extending it to allow interaction and multiple "contexts" to support windows. Like PostScript, NeWS could be used as a complete programming language, but unlike PostScript, NeWS could be used to make complete interactive programs with mouse support and a GUI.
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- "NeWS โ Network Extensible Window System" | 2016-04-12 | 86 Upvotes 74 Comments