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Reverse Video
Reverse video (or invert video or inverse video or reverse screen) is a computer display technique whereby the background and text color values are inverted. On older computers, displays were usually designed to display text on a black background by default. For emphasis, the color scheme was swapped to bright background with dark text. Nowadays the two tend to be switched, since most computers today default to white as a background color. The opposite of reverse video is known as ''true video''. Video is usually reversed by inverting the brightness values of the pixels of the involved region of the display. If there are 256 levels of brightness, encoded as 0 to 255, the 255 value becomes 0 and vice versa. A value of 1 becomes 254, 2 of 253, and so on: ''n'' is swapped for ''r'' - ''n'', for ''r'' levels of brightness. This is occasionally called a ones' complement. If the source image is of middle brightness, reverse video can be difficult to see, 127 becomes 128 for example, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visicalc
VisiCalc (for "visible calculator") is the first spreadsheet computer program for personal computers, originally released for Apple II by VisiCorp on 17 October 1979. It is often considered the application that turned the microcomputer from a hobby for computer enthusiasts into a serious business tool, prompting IBM to introduce the IBM PC two years later. VisiCalc is considered to be Apple II's killer app. It sold over 700,000 copies in six years, and as many as 1 million copies over its history. Initially developed for the Apple II computer using a 6502 assembler running on the Multics time sharing system, VisiCalc was ported to numerous platforms, both 8-bit and some of the early 16-bit systems. In order to do this, the company developed porting platforms that produced bug compatible versions. The company took the same approach when the IBM PC was launched, producing a product that was essentially identical to the original 8-bit Apple II version. Sales were initially brisk, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Favourites
A, or a, is the first letter and the first vowel of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''a'' (pronounced ), plural ''aes''. It is similar in shape to the Ancient Greek letter alpha, from which it derives. The uppercase version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lowercase version can be written in two forms: the double-storey a and single-storey ɑ. The latter is commonly used in handwriting and fonts based on it, especially fonts intended to be read by children, and is also found in italic type. In English grammar, " a", and its variant " an", are indefinite articles. History The earliest certain ancestor of "A" is aleph (also written 'aleph), the first letter of the Phoenician alphabet, which consisted entirely of consonants (for that reason, it is also called an abjad to distinguish it fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Default (computer Science)
A default, in computer science, refers to the preexisting value of a user-configurable setting that is assigned to a software application, computer program or device. Such settings are also called presets or factory presets, especially for electronic devices. Default values are standards values that are universal to all instances of the device or model and intended to make the device as accessible as possible "out of the box" without necessitating a lengthy configuration process prior to use. The user only has to modify the default settings according to their personal preferences. In many devices, the user has the option to restore these default settings for one or all options. Such an assignment makes the choice of that setting or value more likely, this is called the default effect. Examples Application software preferences One use of default parameters is for initial settings for application software. For example, the first time a user runs an application it may suggest that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ones' Complement
The ones' complement of a binary number is the value obtained by inverting all the bits in the binary representation of the number (swapping 0s and 1s). The name "ones' complement" (''note this is possessive of the plural "ones", not of a singular "one"'') refers to the fact that such an inverted value, if added to the original, would always produce an 'all ones' number (the term "complement" refers to such pairs of mutually additive inverse numbers, here in respect to a non-0 base number). This mathematical operation is primarily of interest in computer science, where it has varying effects depending on how a specific computer represents numbers. A ones' complement system or ones' complement arithmetic is a system in which negative numbers are represented by the inverse of the binary representations of their corresponding positive numbers. In such a system, a number is negated (converted from positive to negative or vice versa) by computing its ones' complement. An N-bit ones ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monochrome
A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochromatic light refers to electromagnetic radiation that contains a narrow band of wavelengths, which is a distinct concept. Application Of an image, the term monochrome is usually taken to mean the same as black and white or, more likely, grayscale, but may also be used to refer to other combinations containing only tones of a single color, such as green-and-white or green-and-red. It may also refer to sepia displaying tones from light tan to dark brown or cyanotype ("blueprint") images, and early photographic methods such as daguerreotypes, ambrotypes, and tintypes, each of which may be used to produce a monochromatic image. In computing, monochrome has two meanings: *it may mean having only one color which is either on or off (also known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Description Error
A description error or selection error is an error, or more specifically a human error, that occurs when a person performs the correct action on the wrong object due to insufficient specification of an action which would have led to a desired result. This commonly happens when similar actions lead to different results. A typical example is a panel with rows of identical switches, where it is easy to carry out a correct action (flip a switch) on a wrong switch due to their insufficient differentiation. This error can be very disorienting and usually causes a brief loss of situation awareness or automation surprise if noticed right away. But much worse, if it goes unnoticed, it could cause more serious problems. So allowances such as clearly highlighting a selected item should be made in interaction design. Donald Norman describes the subject in his book ''The Design of Everyday Things''. There he describes how user-centered design User-centered design (UCD) or user-driven deve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ANSI Escape Sequence
ANSI escape sequences are a standard for in-band signaling to control cursor location, color, font styling, and other options on video text terminals and terminal emulators. Certain sequences of bytes, most starting with an ASCII escape character and a bracket character, are embedded into text. The terminal interprets these sequences as commands, rather than text to display verbatim. ANSI sequences were introduced in the 1970s to replace vendor-specific sequences and became widespread in the computer equipment market by the early 1980s. They are used in development, scientific, commercial text-based applications as well as bulletin board systems to offer standardized functionality. Although hardware text terminals have become increasingly rare in the 21st century, the relevance of the ANSI standard persists because a great majority of terminal emulators and command consoles interpret at least a portion of the ANSI standard. History Almost all manufacturers of video termina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accessibility
Accessibility is the design of products, devices, services, vehicles, or environments so as to be usable by people with disabilities. The concept of accessible design and practice of accessible development ensures both "direct access" (i.e. unassisted) and "indirect access" meaning compatibility with a person's assistive technology (for example, computer screen readers). Accessibility can be viewed as the "ability to access" and benefit from some system or entity. The concept focuses on enabling access for people with disabilities, or enabling access through the use of assistive technology; however, research and development in accessibility brings benefits to everyone. Accessibility is not to be confused with usability, which is the extent to which a product (such as a device, service, or environment) can be used by specified users to achieve specified goals with effectiveness, efficiency, convenience, or satisfaction in a specified context of use. Accessibility is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eyestrain
Eye strain, also known as asthenopia (from Greek ''a-sthen-opia'', grc, ἀσθενωπία, ), is a common eye condition that manifests through non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision. Symptoms often occur after long-term use of computers, digital devices, reading or other activities that involve extended visual tasks which are broadly classified into external and internal symptom factors. When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscles and the extraocular muscles are strained. This causes discomfort, soreness or pain on the eyeballs. Closing the eyes for ten minutes and relaxing the muscles of the face and neck at least once an hour usually relieves the problem. A page or photograph with the same image twice, but slightly displaced (from a printing mishap, a camera moving during the shot, etc.) can cause eye strai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flicker (screen)
Flicker is a visible change in brightness between cycles displayed on video displays. It applies to the refresh interval on cathode ray tube (CRT) televisions and computer monitors, as well as plasma computer displays and televisions. Occurrence Flicker occurs on CRTs when they are driven at a low refresh rate, allowing the brightness to drop for time intervals sufficiently long to be noticed by a human eye – see persistence of vision and flicker fusion threshold. For most devices, the screen's phosphors quickly lose their excitation between sweeps of the electron gun, and the afterglow is unable to fill such gaps – see phosphor persistence. A refresh rate of 60 Hz on most screens will produce a visible "flickering" effect. Most people find that refresh rates of 70–90 Hz and above enable flicker-free viewing on CRTs. Use of refresh rates above 120 Hz is uncommon, as they provide little noticeable flicker reduction and limit available resolution. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ocular Larva Migrans
Ocular larva migrans (OLM), also known as ocular toxocariasis, is the ocular form of the larva migrans syndrome that occurs when ''Toxocara canis'' (dog roundworm) larvae invade the eye. They may be associated with visceral larva migrans. Unilateral visual disturbances, strabismus, and eye pain are the most common presenting symptoms. Diagnosis The disease presents with an eosinophilic granulomatous mass, most commonly in the posterior pole of the retina. The granulomatous mass develops around the entrapped larva, in an attempt to contain the spread of the larva. ELISA testing of intraocular fluids has been demonstrated to be of great value in diagnosing ocular toxocariasis. Differential diagnosis The retinal lesion can mimic retinoblastoma in appearance, and mistaken diagnosis of the latter condition can lead to unnecessary ''enucleation''. Complications The eye involvement can cause the following inflammatory disorders: * endophthalmitis * uveitis * chorioretinitis Chorioreti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light-on-dark Color Scheme
A light-on-dark color scheme —also called black mode, dark mode, dark theme, night mode, or lights-out (mode)— is a color scheme that uses light-colored text, icons, and graphical user interface elements on a dark background. It is often discussed in terms of computer user interface design and web design. Many modern websites and operating systems offer the user an optional light-on-dark display mode. Some users find dark mode displays more visually appealing, and claim that it can reduce eye strain. Displaying white on full brightness uses roughly six times as much power as pure black on a 2016 Google Pixel, which has an OLED display. However conventional LED displays cannot benefit from reduced power consumption. Most modern operating systems support an optional light-on-dark color scheme. History Predecessors of modern computer screens, such as cathode-ray oscillographs, oscilloscopes, etc., tended to plot graphs and introduce other content as glowing traces on a bl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
