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L
LAG
Lag is a slow response from a computer. It can be used to describe any computer that is responding slower than expected. However, the term is most commonly used in online gaming.
Video game lag is generally caused by one of two factors – 1) a slow computer or 2) a slow Internet connection. If you are playing an online multiplayer game and your computer cannot process the incoming data in real-time, it may slow the game down for everyone. If your Internet connection is slow or inconsistent (which is common with a shared wireless connection), your system may not send and receive enough data to keep up with other players. This lag may produce choppy frame rates and cause a delay between your input and what happens on the screen.
In an ideal world, all online gamers would have fast computers and fast Internet connections. The reality, however, is that players have a variety of computer systems and significantly different Internet connection speeds. Therefore, video game developers must account for lag in multiplayer games. The preferred method is to make sure lag only affects the individual with the slow computer or Internet connection. This prevents players with high-quality gaming setups from being negatively affected by users with slow systems.
In some cases, a player with a high amount of lag will be booted from a multiplayer game. For example, in StarCraft 2, if a player's system is not responding, a message will appear on the player's screen that says, "Waiting for Server." Other players in the game will see a message that says "Waiting for player: [player name]." If the lag is too high, the player will eventually be booted from the game.
NOTE: "Lag" can also be used as a verb. For example, a player that is "lagging" may be slowing down the game.
Lamp
Stands for "Linux, Apache, MySQL, and PHP." Together, these software technologies can be used to create a fully-functional web server.
Linux is the most popular operating system used in web servers, primarily because many free Linux distributions are available. This means Linux-based servers are typically cheaper to set up and maintain than Windows servers. Since Linux is (open source|open source), it also works with many other popular open source web hosting software components.
The most important software component in the "AMP" package is Apache, or "Apache HTTP Server." Apache is the software that serves webpages over the Internet via the HTTP protocol. Once Apache is installed, a standard Linux machine is transformed into a web server that can host live websites.
Other components of LAMP include MySQL and PHP. MySQL is a popular open source database management system (DBMS) and PHP is a popular web scripting language. Together, these two technologies are used to create dynamic websites. Instead of only serving static HTML pages, a LAMP server can generate dynamic webpages that run PHP code and load data from a MySQL database.
NOTE: In some instances, the "P" in LAMP may stand for either Perl or Python, which are other scripting languages. "AMP" packages for Windows and Mac systems are called WAMP and MAMP respectively.
LAN
Stands for "Local Area Network" and is pronounced "lan." A LAN is a network of connected devices that exist within a specific location. LANs may be found in homes, offices, educational institution, or other areas.
A LAN may be wired, wireless, or a combination of the two. A standard wired LAN uses Ethernet to connect devices together. Wireless LANs are typically created using a Wi-Fi signal. If a router supports both Ethernet and Wi-Fi connections, it can be used to create a LAN with both wired and wireless devices.
Types of LANs
Most residential LANs use a single router to create the network and manage all the connected devices. The router acts as the central connection point and enables devices, such as computers, tablets, and smartphones to communicate with each other. Typically, the router is connected to a cable or DSL modem, which provides Internet access to connected devices.
A computer may also be the central access point of a LAN. In this setup, the computer acts as a server, providing connected machines with access to files and programs located on the server. It also includes LAN software used to manage the network and connected devices. LAN servers are more common in business and educational networks, since the extra capabilities are not required by most home users. In a server-based LAN, devices may connect directly to the server or indirectly via a router or switch.
NOTE: Multiple LANs may be combined to create a larger LAN. This type of network, which can customized to include specific devices from various networks, is called a virtual LAN or VLAN.
Laptop
Laptop computers, also known as notebooks, are portable computers that you can take with you and use in different environments. They include a screen, keyboard, and a trackpad or trackball, which serves as the mouse. Because laptops are meant to be used on the go, they have a battery which allows them to operate without being plugged into a power outlet. Laptops also include a power adapter that allows them to use power from an outlet and recharges the battery.
While portable computers used to be significantly slower and less capable than desktop computers, advances in manufacturing technology have enabled laptops to perform nearly as well as their desktop counterparts. In fact, high-end laptops often perform better than low or even mid-range desktop systems. Most laptops also include several I/O ports, such as USB ports, that allow standard keyboards and mice to be used with the laptop. Modern laptops often include a wireless networking adapter as well, allowing users to access the Internet without requiring any wires.
While laptops can be powerful and convenient, the convenience often comes at a price. Most laptops cost several hundred dollars more than a similarly equipped desktop model with a monitor, keyboard, and mouse. Furthermore, working long hours on a laptop with a small screen and keyboard may be more fatiguing than working on a desktop system. Therefore, if portability is not a requirement for your computer, you may find better value in a desktop model.
Laser Printer
A laser printer is a printer that uses a focused beam or light to transfer text and images onto paper. Though contrary to popular belief, the laser does not actually burn the images onto the paper. Instead, as paper passes through the printer, the laser beam fires at the surface of a cylindrical drum called a photoreceptor. This drum has an electrical charge (typically positive), that is reversed in areas where the laser beam hits it. By reversing the charge in certain areas of the drum, the laser beam can print patterns (such as text and pictures) onto the photoreceptor.
Once the pattern has been created on the drum, it is coated with toner from a toner cartridge. The toner is black in most cartridges, but may be cyan, magenta, and yellow in color laser printers. The positively charged toner clings to areas of the drum that have been negatively charged by the laser. When the paper passes through the printer, the drum is given a strong negative charge, which allows the toner to transfer and stick to the paper. The result is a clean copy of the image written on the paper.
Because laser printers do not use ink, they have less image smearing problems than inkjet printers and are able to print pages faster. While laser printers and toner cartridges typically cost more than inkjet printers and ink cartridges, most laser toner cartridges last several times longer than ink cartridges, which makes their cost per page about equal. For this reason, businesses tend to use laser printers, while consumers are more likely to use inkjet printers. Laser printers typically have a resolution of 600 dpi (dots per inch) or higher.
Latency
In computing, "latency" describes some type of delay. It typically refers to delays in transmitting or processing data, which can be caused by a wide variety of reasons. Two examples of latency are network latency and disk latency, which are explained below.
1. Network latency
Network latency describes a delay that takes place during communication over a network (including the Internet). For example, a slow router may cause a delay of a few milliseconds when one system on a LAN tries to connect to another through the router. A more noticeable delay may happen if two computers from different continents are communicating over the Internet. There may be a delay in simply establishing the connection because of the distance and number of "hops" involved in making the connection. The "ping" response time is a good indicator of the latency in this situation.
2. Disk latency
Disk latency is the delay between the time data is requested from a storage device and when the data starts being returned. Factors that effect disk latency include the rotational latency (of a hard drive) and the seek time. A hard drive with a rotational speed of 5400 RPM, for example, will have almost twice the rotational latency of a drive that rotates at 10,000 RPM. The seek time, which involves the physical movement of the drive head to read or write data, can also increase latency. Disk latency is why reading or writing large numbers of files is typically much slower than reading or writing a single contiguous file. Since SSDs do not rotate like traditional HDDs, they have much lower latency.
Other types of latency
Many of other types of latency exist, such as RAM latency (a.k.a. "CAS latency"), CPU latency, audio latency, and video latency. The common thread between all of these is some type of bottleneck that results in a delay. In the computing world, these delays are usually only a few milliseconds, but they can add up to create noticeable slowdowns in performance.
NOTE: It is important to not confuse latency with other measurements like data transfer rate or bandwidth. Latency refers to the delay before the data transfer starts rather than the speed of the transfer itself.
Lazy loading
Lazy loading is a programming technique that delays loading resources until they are needed. A common example is a webpage that defers loading images until the user scrolls to their location within the page. Lazy loading is used on the web and in software programs, such as mobile and desktop applications.
Lazy Loading on the Web
Lazy loading images within a webpage can speed up the load time since the browser does not need to load images that are not visible. As the user scrolls through the page, the images are loaded dynamically. This is accomplished using JavaScript that detects the position of each image and determines if it is in the browser window's viewable area. If the user scrolls down to an image, the JavaScript will request the resource from the web server and display the image on the page. If the user does not scroll down, the image will not load.
It is possible to delay the loading of other resources, such as JavaScript files, CSS, and even the HTML itself. For example, a web developer might determine which CSS styles are needed for "above-the-fold" content on a webpage, or content viewable within the height of a typical browser window. The developer can implement these as "inline styles," or styles defined within the HTML of the webpage. JavaScript is used to load additional CSS after the page has loaded or once the user starts scrolling.
Lazy loading video is also popular on the web. It is especially effective since video files are typically the largest resources loaded within a webpage. Instead of sending the entire video to a client's device, the web server only sends small portions of the video while the user is watching it. Popular video sharing websites like YouTube and Vimeo use lazy loading to reduce bandwidth and to prevent users from downloading more video content than necessary. This is especially helpful for users with metered Internet connections, such as mobile data plans.
When lazy loading a video, it is common to load a few seconds or even several minutes ahead of the current point in the video. The video data is saved in a buffer, which helps videos play smoothly even when the Internet connection is not consistent.
Lazy Loading in Software Programs
While lazy loading has become increasingly popular on the web, it has been used in software development for a long time. For example, an operating system may only display thumbnail images for the visible icons in a folder. Similarly, an image viewing program may only load the visible images in a photo library. This uses less memory and improves application performance because the program does not load unnecessary data.
LCD
Stands for "Liquid Crystal Display." LCD is a flat panel display technology commonly used in TVs and computer monitors. It is also used in screens for mobile devices, such as laptops, tablets, and smartphones.
LCD displays don't just look different than bulky CRT monitors, the way they operate is significantly different as well. Instead of firing electrons at a glass screen, an LCD has backlight that provides light to individual pixels arranged in a rectangular grid. Each pixel has a red, green, and blue RGB sub-pixel that can be turned on or off. When all of a pixel's sub-pixels are turned off, it appears black. When all the sub-pixels are turned on 100%, it appears white. By adjusting the individual levels of red, green, and blue light, millions of color combinations are possible.
How an LCD works
The backlight in liquid crystal display provides an even light source behind the screen. This light is polarized, meaning only half of the light shines through to the liquid crystal layer. The liquid crystals are made up of a part solid, part liquid substance that can be "twisted" by applying electrical voltage to them. They block the polarized light when they are off, but reflect red, green, or blue light when activated.
Each LCD screen contains a matrix of pixels that display the image on the screen. Early LCDs had passive-matrix screens, which controlled individual pixels by sending a charge to their row and column. Since a limited number of electrical charges could be sent each second, passive-matrix screens were known for appearing blurry when images moved quickly on the screen. Modern LCDs typically use active-matrix technology, which contain thin film transistors, or TFTs. These transistors include capacitors that enable individual pixels to "actively" retain their charge. Therefore, active-matrix LCDs are more efficient and appear more responsive than passive-matrix displays.
NOTE: An LCD's backlight may either be a traditional bulb or LED light. An "LED display" is simply an LCD screen with an LED backlight. This is different than an OLED display, which lights up individual LEDs for each pixel. While the liquid crystals block most of an LCD's backlight when they are off, some of the light may still shine through (which might be noticeable in a dark room). Therefore OLEDs typically have darker black levels than LCDs.
LDAP
Stands for "Lightweight Directory Access Protocol." If you want to make directory information available over the Internet, this is the way to do it. LDAP is a streamlined version of an earlier directory standard called X.500. What makes LDAP so useful is that it works great over TCP/IP networks (unlike X.500), so information can be accessed through LDAP by anyone with an Internet connection. It is also an open protocol, which means directories can be stored on any type of machine (i.e. Windows 2000, Red Hat Linux, Mac OS X).
To give you an idea of how an LDAP directory is organized, here are the different levels of a simple LDAP tree hierarchy:
- The root director
- Countries
- Organizations
- Divisions, departments, etc.
- Individuals
- Individual resources, such as files and printers.
EXAMPLE: A user can import an email address book into
a recent version of Microsoft Outlook.
Most LDAP connectivity is done behind the scenes, so the typical user probably won't notice it when surfing the Web. However, it is a good technology to know about. If nothing else, it is another term to impress your parents with.
Lead
Lead (pronounced "leed") is a marketing term that describes a connection made with a potential customer or client. The goal of most online advertising is to generate leads, which may "lead" to sales or subscriptions for a company or organization.
The process of creating leads on the Internet is called online lead generation. This can be accomplished by running ads through a service like Google AdWords or Bing Ads or by directly purchasing advertising space on other websites. Advertisers can choose to run either CPC (cost per click) or CPA (cost per action) ads, which can both generate leads. While CPA and CPL (cost per lead) are often used interchangeably, CPL specifically measures lead generations, rather than aggregate clicks or sales.
A typical online lead is created when a user fills out and submits a form on a website. The number of fields required depends on the type of lead. For example, an automotive dealer website may provide an online form for interested buyers. The form may request your name, email address, physical address, phone number, and best time to reach you. Other forms are more basic and only capture an email address. These types of leads are often created when you sign up for a newsletter or download a software program. Whatever information is captured in a lead can be used to contact you at a later time for marketing purposes.
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