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Technical Corner => The PC Glossary - Definitions of Computer and Internet Terms => Topic started by: MysteRy on April 04, 2014, 07:43:04 AM

Title: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:43:04 AM

Source : PC.net (http://pc.net/glossary/)

LAN

Stands for "Local Area Network," and is pronounced like "land" without the "d". (Computer people will think you're weird if you pronouce it "L-A-N"). A LAN is a computer network limited to a small area such as an office building, university, or even a residential home. Most mid to large-sized businesses today use LANs, which makes it easy for employees to share information. Currently, the most common type of LANs are Ethernet-based and use software from Novell or Oracle. However, with the emergence of wireless networking, wireless LANs have become a popular alternative.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:43:50 AM

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.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:44:38 AM

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.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:45:25 AM

Latency

This is the amount of time it takes a packet of data to move across a network connection. When a packet is being sent, there is "latent" time, when the computer that sent the packet waits for confirmation that the packet has been received. Latency and bandwidth are the two factors that determine your network connection speed.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:46:22 AM

LCD

Stands for "Liquid Crystal Display." LCDs are super-thin displays that are used in laptop computer screens and flat panel monitors. Smaller LCDs are used in handheld TVs, PDAs, and portable video game devices. The image on an LCD screen is created by sandwiching an electrically reactive substance between two electrodes. This color of this substance can be changed by increasing or reducing the electrical current. Since LCD screens are based on the principle of blocking light (rather than emitting it), they use up much less power than standard CRT (Cathode-Ray Tube) monitors.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:47:14 AM

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 directory
Countries
Organizations
Divisions, departments, etc.
Individuals
Individual resources, such as files and printers.

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.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:47:55 AM

Leaderboard

As the average computer screen size has grown larger, the size of online advertisements as grown as well. The leaderboard ad, which was introduced in 2003, has a standard size of 728 pixels wide by 90 pixels tall (728x90). Compare that to its predecessor, the banner ad, which is 468 pixels wide by 60 pixels tall (468x60).

Leaderboards can contain text, images, or even animations. When a visitor clicks on a leaderboard, he or she is directed to the advertiser's website. While leaderboards are larger than the original banner ads, most Web developers have found ways to incorporate the ads in ways that are not too distracting to the user.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:49:22 AM

Leaf

What does a computer's hard disk have in common with a tall oak? While it may not look like a tree on the outside, the hard disk is organized the same way. Directories of files and folders on a hard drive are organized into branches, where each directory is a branch with files and folders. Folders make up the branches, while files are the leaves. Therefore a leaf is a file within a directory on your hard drive.

Technically speaking, a leaf is a node on a tree with no child nodes. Because files cannot have child nodes like folders can, they are always leafs. When referring to a tree structure, a leaf can also be called a leaf node.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:50:22 AM

LED

Example: "Many modern cars use LEDs for their brake lights."

LED is short for "Light-Emitting Diode." It is a type of electronic light source that is activated by an electrical current. LEDs are highly energy-efficient and last much longer than traditional light bulbs. They can used for indicator lights, clock displays, street lights, and many other applications. LEDs have also begun to replace traditional bulbs as the backlight source in LCD monitors and TVs.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:51:17 AM

LIFO

Stands for "Last In, First Out." LIFO is a method of processing data in which the last items entered are the first to be removed. This is the opposite of LIFO is FIFO (First In, First Out), in which items are removed in the order they have been entered.

To better understand LIFO, imagine stacking a deck of cards by placing one card on top of the other, starting from the bottom. Once the deck has been fully stacked, you begin to remove the cards, starting from the top. This process is an example of the LIFO method, because the last cards to be placed on the deck are the first ones to be removed.

The LIFO method is sometimes used by computers when extracting data from an array or data buffer. When a program needs to access the most recent information entered, it will use the LIFO method. When information needs to be retrieved in the order it was entered, the FIFO method is used.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:52:19 AM

Link

When you are browsing the Web and you see a highlighted and underlined word or phrase on a page, there is a good chance you are looking at a link. By clicking on a link, you can "jump" to a new Web page or a completely different Web site. While text links are typically blue and underlined, they can be any color and don't have to be underlined. Images can also serve as links to other Web pages. When you move the cursor over a link in a Web page, the arrow will turn into a little hand, letting you know that it is a link. The term "hypertext" comes from the way links can quickly send you to another Web destination.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:53:19 AM

LinkedIn

Example: "She uses LinkedIn to keep track of all her business contacts."

LinkedIn is a business-oriented social networking website. It allows you to create a custom profile and add other LinkedIn users to your list of connections. Unlike Facebook, LinkedIn profiles are designed to be professional, rather than personal. They appear like a resume, with education and work experience being the most prominent. By using LinkedIn, you can keep in touch with past colleagues and meet new potential business partners.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:54:11 AM

Linux

Example: "Web servers commonly run the Linux operating system."

Linux is a free, open source, Unix-like operating system. It is available in several different distributions, including CentOS, Debian, Ubuntu, and Red Hat. Linux can run on several different hardware platforms and may even be used as the OS for electronics devices besides computers. Though Linux is not commonly installed on home computers, it is widely used by Web hosting companies and has many other specialized applications.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:55:07 AM

Listserv

This term looks like it's missing an "e", but that's how it's spelled. A listserv, or list server, is a small program that automatically sends messages to multiple e-mail addresses on a mailing list. When someone subscribes to a mailing list, the listserv will automatically add the address and distribute future e-mail messages to that address along with all the others on the list. When someone unsubscribes, the listserv simply removes the address. At least that is the way it supposed to work. Unfortunately, with some SPAM lists, unsubscribing only adds you to more lists.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:56:10 AM

Load Balancing

Computer networks are complex systems, often routing hundreds, thousands, or even millions of data packets every second. Therefore, in order for networks to handle large amounts of data, it is important that the data is routed efficiently. For example, if there are ten routers within a network and two of them are doing 95% of the work, the network is not running very efficiently. The network would run much faster if each router was handling about 10% of the traffic. Likewise, if a website gets thousands of hits every second, it is more efficient to split the traffic between multiple Web servers than to rely on a single server to handle the full load.

Load balancing helps make networks more efficient. It distributes the processing and traffic evenly across a network, making sure no single device is overwhelmed. Web servers, as in the example above, often use load balancing to evenly split the traffic load among several different servers. This allows them to use the available bandwidth more effectively, and therefore provides faster access to the websites they host.

Whether load balancing is done on a local network or a large Web server, it requires hardware or software that divides incoming traffic among the available servers. Networks that receive high amounts of traffic may even have one or more servers dedicated to balancing the load among the other servers and devices in the network. These servers are often called (not surprisingly) load balancers.

Clusters, or mulitple computers that work together, also use load balancing to spread out processing jobs among the available systems.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:57:33 AM

Localhost

"Localhost" refers to the local computer that a program is running on. For example, if you are running a Web browser on your computer, your computer is considered to be the "localhost." While this does not need to be specified when using a single computer, the localhost does need to be defined when running programs from multiple computers. For example, a network administrator might use his local machine to start a Web server on one system and use a remote access program on another. These programs would run from computers other than the localhost.

In the example above, the two non-local computers must be defined by their IP addresses. The local machine is defined as "localhost," which gives it an IP address of 127.0.0.1. This is considered a "loopback" address because the information sent to it is routed back to the local machine. Localhost is often used in Web scripting languages like PHP and ASP when defining what server the code should run from or where a database is located.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 07:58:48 AM

Log File

Example: "The list of installed files is saved in a log file."

A log file contains a record of events generated by a software program or output by a hardware device. Most log files are saved in a plain text format, which allows them to viewed in a basic text editor. Log files may be generated by Web servers, software installers, or a variety of applications. The data stored in a log file can be used to troubleshoot software issues or run reports.

Most log files have a .LOG file extension.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 08:00:00 AM

Logic Gate

Logic gates perform basic logical functions and are the fundamental building blocks of digital integrated circuits. Most logic gates take an input of two binary values, and output a single value of a 1 or 0. Some circuits may have only a few logic gates, while others, such as microprocessors, may have millions of them. There are seven different types of logic gates, which are outlined below.

In the following examples, each logic gate except the NOT gate has two inputs, A and B, which can either be 1 (True) or 0 (False). The resulting output is a single value of 1 if the result is true, or 0 if the result is false.

1. AND - True if A and B are both True

2. OR - True if either A or B are True

3. NOT - Inverts value: True if input is False; False if input is True

4. XOR - True if either A or B are True, but False if both are True

5. NAND - AND followed by NOT: False only if A and B are both True

6. NOR - OR followed by NOT: True only if A and B are both False

7. XNOR - XOR followed by NOT: True if A and B are both True or both False

By combining thousands or millions of logic gates, it is possible to perform highly complex operations. The maximum number of logic gates on an integrated circuit is determined by the size of the chip divided by the size of the logic gates. Since transistors make up most of the logic gates in computer processors, smaller transistors mean more complex and faster processors.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 08:03:51 AM

Login

If you are ever asked to enter your username and password, you are being asked to enter your login information. A login is a combination of information that authenticates your identity. This could be a name and password or an ID number and security code. Many secure Web sites use login information to authenticate visitors before allowing them access to certain areas of the site. Unlike the words "brush" and "comb," this term should not be used as both a noun and a verb. It should only be used as a noun, (you don't login to a server, you log in to it).

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 08:04:56 AM

Lossless

Lossless compression reduces a file's size with no loss of quality. This seemingly magical method of reducing file sizes can be applied to both image and audio files. While JPEGs and MP3s use lossy compression, newer compression algorithms, such as JPEG 2000 and Apple Lossless compression, can be used to create lossless compressed files.

Lossless compression basically rewrites the data of the original file in a more efficient way. However, because no quality is lost, the resulting files are typically much larger than image and audio files compressed with lossy compression. For example, a file compressed using lossy compression may be one tenth the size of the original, while lossless compression is unlikely to produce a file smaller than half of the original size.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 08:05:54 AM

Lossy

Lossy file compression results in lost data and quality from the original version. Lossy compression is typically associated with image files, such as JPEGs, but can also be used for audio files, like MP3s or AAC files. The "lossyness" of an image file may show up as jagged edges or pixelated areas. In audio files, the lossyness may produce a watery sound or reduce the dynamic range of the audio.

Because lossy compression removes data from the original file, the resulting file often takes up much less disk space than the original. For example, a JPEG image may reduce an image's file size by more than 80%, with little noticeable effect. Similarly, a compressed MP3 file may be one tenth the size of the original audio file and may sound almost identical.

The keyword here is "almost." JPEG and MP3 compression both remove data from the original file, which may be noticeable upon close examination. Both of these compression algorithms allow for various "quality settings," which determine how compressed the file will be. The quality setting involves a trade-off between quality and file size. A file that uses greater compression will take up less space, but may not look or sound as good as a less compressed file. Some image and audio formats allow lossless compression, which does not reduce the file's quality at all.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 08:06:53 AM

LPI

Stands for "Lines Per Inch." LPI is used to measure the resolution of images printed in halftones. Because halftone images are printed as a series of dots, the higher the LPI number, the more dense the dots can be, resulting in a finer resolution.

Newspapers are typically printed in a resolution of 85 lpi, while magazines may use 133 lpi or higher. Because the naked eye can distinguish halftone dots up to about 120 lpi, you are more likely to notice the dots in newspaper print than in magazines. Of course, if you look closely enough, you may be able to see the dots in images printed in 150 lpi or more. But, in normal viewing, it is natural to see the dots as a continuous image even at 85 lpi.

Title: Re: Computer Terms Beginning with "L"
Post by: MysteRy on April 04, 2014, 08:07:46 AM

LUN

Stands for "Logical Unit Number." LUNs are used to identify SCSI devices, such as external hard drives, connected to a computer. Each device is assigned a LUN, from 0 to 7, which serves as the device's unique address.

LUNs can also be used for identifying virtual hard disk partitions, which are used in RAID configurations. For example, a single hard drive may be partitioned into multiple volumes. Each volume can then be assigned a unique LUN. However, few modern computers use LUNs, since SCSI devices have mostly been replaced by USB and Firewire devices.