Machine language

more websites at www.nitchsites.net

page 1 | page2 | page3| home

Slide rule The slide rule is a mechanical precursor of the pocket calculator. It was invented in 1625 by William Oughtred. Once widely used for rapid, approximate scientific and engineering calculations, a slide rule is an analog computer consisting of three interlocking calibrated strips. The central strip can be moved lengthways relative to the other two. A sliding cursor with an alignment line can record an intermediate result on any of the scales. One slide rule remains in daily use around the world, the E-6B. This is a circular slide rule first created in the 1930s for pilots to help with dead-reckoning. It is still available in all flight shops, and remains widely used. While GPS has greatly reduced the use of dead-reckoning for aerial navigation, the E-6B remains widely used as a backup device and all flight schools demand its use. Theory of operation Slide rules calibrated on one side were called "simplex." Slide rules calibrated on both sides were called "duplex." Typically two significant figures of precision were possible, with three being obtained by expert users who could estimate the fraction between gradations. Some high-end slide rules had magnifying cursors that basically doubled the accuracy, permitting a 10 inch slide rule to serve as well as a 20 inch. Slide rules often have other mathematical functions encoded on other auxiliary scales. The most popular were trigonometric, usually sine and tangent, logarithm of logarithm (base 10) (for taking the log of a value on a multiplier scale), natural logarithm and exponential scales. Some rules included a pythagorean scale, to figure sides of traiangles, and a scale to figure circles. Specialised slide rules were invented for various forms of engineering, business and banking. These often had common calculations directly expressed as special scales, for example loan calculations, optimal purchase quantities, or particular engineering equations. A number of tricks were used to get more convenience. Trigonometric scales were sometimes dual-labelled, in black and red, with complementary angles, the so-called "Darmstadt" style. Duplex slide rules often duplicated basic scales on the back. Scales were often "split" to get higher accuracy. Circular slide rules had two basic types, one with two cursors, and another with a moveable disk and a cursor. The basic advantage of a circular slide rule is that the longest dimension was reduced by a factor of about 3 (i.e. by π). For example, a 10cm circular would have a maximum accuracy equal to a 30cm ordinary slide rule. Circular slide rules were mechanically more rugged, smoother-moving and more precise than linear slide rules, because they depended on a single central bearing. The central pivot did not usually fall apart. The pivot also prevented scratching of the face and cursors. Only the most expensive linear slide rules had these features. The highest accuracy scales were placed on the outer rings. Rather than "split" scales, high-end circular rules used helical (snail-shell-shaped) scales for difficult things like log-of-log scales. One eight-inch premium circular rule had a 50 inch helical log-log scale! Circular slide rules also eliminate "off-scale" calculations, because the scales were designed to "wrap around." A real disadvantage of circular slide rules is that less-important scales are closer to the center, and have lower accuracies. The main disadvantage of circular slide rules was just that they were not standard. Most students learned on the linear slide rules, and never switched. Materials The best older slide rules were made of bamboo, which is dimensionally stable, strong and naturally self-lubricating. They used scales of celluloid or plastic. Some were made of mahogany. Later slide rules were made of plastic, or aluminum painted with plastic. All premium slide rules had numbers and scales engraved, and then filled with paint or other resin. Painted or imprinted slide rules are inferior because the markings wear off. Early cursors were metal frames holding glass. Later cursors were acrylics or polycarbonates sliding on teflon bearings. Magnifying cursors can both help engineers with bad eyes, and double the accuracy of a slide rule. Premium slide rules included clever catches so the rule would not fall apart by accident, and bumpers so that tossing the rule on the table would not scratch the scales or cursor. The recommended cleaning method for engraved markings is light scrubbing with steel-wool. For painted slide rules, and the faint of heart, use diluted commercial window-cleaning fluid and a soft cloth. History Slide rules came into wide use in the 1850s, as engineering became a recognized professional activity. In World War II, bombardiers, navigators, and other warriors who required quick calculations often used specialized slide rules. One office of the U.S. Navy actually designed a generic slide rule "chassis" with an aluminum body and plastic cursor into which celluloid cards (printed on both sides) could be placed for special calculations. The process was invented to calculate range, fuel-use and altitude for aircraft, and then adapted to many other purposes. Throughout the 1950s and 1960s the slide rule was the symbol of the engineer's profession in the same way that the stethoscope symbolized the medical profession. Some engineering students and engineers actually carried 5 inch pocket slide rules in their belts, in addition to using a 10 or 20Êinch rule for precision work at home or at the office. All this came to an end in the 1970s, when the advent of miniaturised scientific calculators made slide rules obsolete. Most slide rules are now collectors' items. A very popular model is the Keuffel & Esser Deci-Lon, a premium scientific & engineering slide rule, available in tenÊinch "regular" and fiveÊinch "pocket" variants. Another prized model is the eightÊinch Scientific Instruments circular slide rule. At the turn of the millennium, the collectors' market still doesn't seem to be drying up, and as recently as 2002, new slide rules were being located in the back-shelves of university book-stores, even though production ended in 1973.

Basic GUI Terminology Knowing What You're Working With Helps Technicians Getting help with your computer software can be easier when you know the correct terms to use. One of the biggest problems that new computer users have with technical support is not knowing how to correctly describe the problem that they're having. And it isn't fair to expect a tech support person to automatically know what a "thing-a-ma-jingy," or "whatcha-ma-call-it" is. The following describes the correct names for common components of software so that when you experience a problem, you can effectively describe an issue that you're having and a technician can readily resolve it. User interface - this is the visual design of a program. It may contain squares, boxes, words, icons, and buttons. If you're experiencing insufficient memory for example, you might see black rectangles across the user interface of your software programs. Title bar - this is the top-most part of a program that displays its own name or it may describe the contents displayed in another part of the interface. If a program is incorrectly coded, you may see a wrong description in this part of its interface. Menu bar - this part of a program displays menu items and menu options. Some of the most common parts of a menu bar grants access to File commands, Open commands, Save commands, and Print commands. An example of an error in this part of an interface would be if an option was missing or grayed out (lighter in color). Tool bar - this part of a program displays small icons across the top which represent tools. Clicking an icon will open a tool or process a command that might also exist on a program's menu bar. Problems in this part of an interface are uncommon, however if you find yourself repeatedly clicking an icon with no results, you can correctly describe the problem by referring to the toolbar. Minimize, Restore, and Exit buttons - these three buttons are usually located on the right-most upper part of a program's interface and each allow you to minimize a program's screen, restore it to its original size, or shut down the program completely. Scroll bar - this convenient tool allows users to move data up and down the computer screen. Status bar - this part of a program is located at the bottom-most part of its interface, and it usually displays small messages that indicate the progress of a command or task. If programmed incorrectly, an application might display the wrong information in this area. Context menu - like the menu bar, a context menu displays when a user right-clicks on something. It displays commands just like what you see on a File menu or a Help menu. Input box - input boxes are usually small rectangles that allow you to type data into a simple interfaces like a webpage or browser window. If you find that you can't type information into one of these, you can effectively resolve the issue with a technician by calling it an input box, rather than a "white rectangle," or "place to put in text." Button - buttons perform a command after a user clicks them with a mouse. Problems occur when the text of a button is grayed out or if it doesn't appear to sink into the screen when clicked. Check box - a check box is a small box that allows a user to indicate several choices among many. When clicked, a small "x" displays inside a box. Similar to the check box, a radio button allows a user to indicate a single choice among many. Problems with radio buttons and check boxes occur when a user makes one choice, but the interface reacts as if the user made many choices (or none at all). When describing a problem to a technician, be sure to indicate whether the problem occurs with a check box or a radio box. Computer novices mistakenly interchange the names of both of these controls. You are granted reprint rights to the articles as long as they contain the following author: (Jim Boxley) Please visit my website at: http://www.nitchsites.net or http://www.articleshopp.com (You are granted the right to reprint this article but the title and content must remain unchanged and the authors name and contact information must be included.) ** Attn Ezine editors / Web site owners ** Feel free to reprint this article in its entirety in your ezine, blog, or on your web site so long as you include the author's resource box above.