| Word | Description |
| L1 cache (Level 1 Cache) | A small piece of very fast memory that’s almost always on the CPU chip itself. It sits between the CPU registers and the L2 cache. Typically L1 cache has a lower latency than L2 cache, making it more expensive to produce and harder to produce in larger quantities without additional complexity. |
| L2 cache (Level 2 Cache) | A piece of fast memory that sits between the L1 cache of the processor and main memory. It is usually larger than L1 cache, and the L1 cache checks the L2 cache before going to main memory for data (unless the L1 and L2 caches are unified–see unified cache). Nowadays L2 caches are almost always on the same die as the microprocessor, but they can be off-chip. |
| L3 Cache (Level 3 Cache) | This type of cache is becoming more prevalent as microprocessor manufacturers ship more processors with L1 and L2 cache built into the processor. L3 cache is then the extra cache that sits on the motherboard between the processor and main memory, since the processor already contains L1 and L2 cache. Some processors are starting to ship with L3 cache built-in as well to speed up memory operations further. In those cases the L3 cache often sits on a separate area of the die, not built directly into the chip core. |
| Lag | A condition caused by network congestion. When more traffic is flowing than a network or connection can handle, it causes programs waiting to send or receive data over the network to slow down, or lag. This term is often used to describe a slowdown while playing games online, especially over dial-up modems or any connection with high latency. |
| LAMP | Linux, Apache, MySQL and PHP. Also defined as Linux, Apache, MySQL and Pythor or Perl. The term LAMP is used to describe a web based solution produced using PHP (scripting), MySQL (database), Apache (web-server) under Linux (operating system), each of which are free to download. It therefore describes a website using free off-the-shelf components. |
| LAN | Local Area Network. Usually a high speed network, normally confined to a single geographic area, allowing communications at either 10Mbps, 100Mbps or (rarely but up-coming) 1000Mbps. cf WAN. LANs are typically implemented using Ethernet, Token Ring, Fast Ethernet, Fibre Distributed Interface (FDDI), Asynchronous Transfer Mode (ATM) or LocalTalk. |
| 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. |
| Large Scale Integration (LSI) | This refers to chips containing thousands of transistors–but less than a million. See also ULSI, VLSI, MSI, and SSI. |
| 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 | 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. |
| Lattice Techniques | Lattice Techniques use security designations to determine access to information. |
| Layer 2 Forwarding Protocol (L2F) | An Internet protocol (originally developed by Cisco Corporation) that uses tunneling of PPP over IP to create a virtual extension of a dial-up link across a network, initiated by the dial-up server and transparent to the dial-up user. |
| Layer 2 Tunneling Protocol (L2TP) | An extension of the Point-to-Point Tunneling Protocol used by an Internet service provider to enable the operation of a virtual private network over the Internet. |
| LCD | Liquid Crystal Display. cf CRT. |
| LDAP | Lightweight Directory Access Protocol. An implementation of the industry standard X.500 directory protocol developed for PCs and the internet. Unlike X.500, LDAP is designed for IP, has a small footprint, is simple to implement and is faster and less network-intensive than X.500. Also abbreviated to "LDap". Put simply, LDAP is a protocol for querying directory services (such as the Windows Active Directory or DNS servers) over TCP/IP. |
| Leased Line | Refers to line such as a telephone line or fiber-optic cable that is rented for exclusive 24-hour, 7-days-a-week use from your location to another location. The highest speed data connections require a leased line. |
| Least Privilege | Least Privilege is the principle of allowing users or applications the least amount of permissions necessary to perform their intended function. |
| LED | Light Emitting Diode. Small light found on many items of equipment, typically used to indicate activity or that something is switched on. Cheap and low power. Typically red in colour (because these are cheaper to produce) but available in other colours also. cf OLED. |
| Legacy device | A type of device or peripheral that is not Plug-and-Play-compatible. Such devices often contain jumpers that must be set manually. |
| Legacy System | Any old computer system that was set up before your time and now continues to work and need support. Often legacy systems are problematic to upgrade because the people that put them together aren’t around any more. One great example was the Year 2000 problem. Legacy systems were driving everyone nuts because no one programmed in COBOL anymore, and lots of legacy code was written in COBOL. |
| License (Software license) | Most corporations need multiple copies of software, but do not need the media in which they come, either because they already have it or because they allow users to install software from a server on the network. Companies still need to purchase a copy for each user, however, so they need a way to prove they have actually purchased a copy of each. These companies purchase software licenses with no associated media. Such licenses are typically just sheets of paper that cost a lot of money, but allow you to legally use additional copies of the software. |
| Lightweight Directory Access Protocol (LDAP) | An industry standard open client/server protocol for accessing a directory service, such as Active Directory or Novell Directory Services. It is a simplified version of the X.500 protocol. |
| Line in | An analog I/O port for a sound device that allows a device to receive a line-level audio signal. A line-level signal is a non-amplified sound signal meant to be sent to a device that has a line-in port. Since the line-level signal isn’t amplified it is typically cleaner. |
| Line out | An analog I/O port for a sound device that allows a device to send a line-level audio signal. This is opposed to an amplified signal on a speaker out port. |
| LINK "ROT" | Term used to describe the frustrating and frequent problem caused by the constant changing in URLs. A Web page or search tool offers a link and when you click on it, you get an error message (e.g., "not available") or a page saying the site has moved to a new URL. Search engine spiders cannot keep up with the changes. URLs change frequently because the documents are moved to new computers, the file structure on the computer is reorganized, or sites are discontinued. If there is no referring link to the new URL, there is little you can do but try to search for the same or an equivalent site from scratch. |
| Link State | With link state, routes maintain information about all routers and router-to-router links within a geographic area, and creates a table of best routes with that information. |
| Links | These are the hypertext connections between Web pages. This is a synonym for hotlinks or hyperlinks. |
| Linksys | Linksys by Cisco, commonly known as Linksys, is a major provider of home and small office network products and was founded in 1988 and acquired by Cisco Systems in 2003[1]. Linksys also manufactures broadband and wireless routers, consumer and small business grade Ethernet switching, VoIP equipment, wireless internet video camera, AV products, network storage systems, and other products. Since 2008, all Linksys products sold are now packaged and branded as "Linksys by Cisco". |
| Linux | A widely used Open Source Unix-like operating system. Linux was first released by its inventor Linus Torvalds in 1991. There are versions of Linux for almost every available type of computer hardware from desktop machines to IBM mainframes. The inner workings of Linux are open and available for anyone to examine and change as long as they make their changes available to the public. This has resulted in thousands of people working on various aspects of Linux and adaptation of Linux for a huge variety of purposes, from servers to TV-recording boxes. |
| Liquid Cooling | This form of cooling refers to water cooling, or any other method of cooling where a liquid is used to keep something cool. |
| List Based Access Control | List Based Access Control associates a list of users and their privileges with each object. |
| LISTSERV, Listserver | An electronic mailing list; it provides a simple way of communicating with a large number of people very quickly by automating the distribution of electronic mail. At OSU, mailing lists are used not only for scholarly communication and collaboration, but also as a means of facilitating and enhancing classroom education. |
| Live Backup | The operation of copying a whole virtual machine, while powered on, at the host OS level, for archiving purposes. |
| Live Migration | The operation of moving a virtual machine, while powered on, from a host OS to another host OS, for maintenance or server consolidation purposes. |
| LMZ | Local Machine Zone. One of the default security zones that Microsoft's Internet Explorer uses. It includes anything that exists on the local computer (other than cached pages). |
| 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. |
| Loadable Kernel Modules (LKM) | Loadable Kernel Modules allow for the adding of additional functionality directly into the kernel while the system is running. |
| 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. |
| Log | 1. The act of writing information to a log (see definition 2) or to a log file. The term originates from the practise of a maritime officer maintaining a record of events in a ship's log. 2. A record of what has happened, i.e. a record of events. Historically a written diary, such as a captains log recording events on a voyage. In this context it can also refer to a log file. 3. Abbreviation for logarithm, a mathematical function. |
| Log Clipping | Log clipping is the selective removal of log entries from a system log to hide a compromise. |
| Log file | A file that contains a record of activities that have occurred. An application is said to "log" information to the log file (hence the name "log file"). Log files are generated automatically by some applications as they work and are typically (but not always) text editable files. Text editable (and therefore human readable) log files are typically generated produced to provide a record of what went on and are not normally used again by the application that generated them. Databases in particular will generate log files in a binary format which are intended for its own database recovery purposes and are not intended for human reading. Log files will typically have the file extension of .log, but this is not guaranteed and depends on the application. |
| log in, log on | The process of entering your username and password to gain access to a particular computer; e.g., a mainframe, a network or secure server, or another system capable of resource sharing. |
| Logic Gate | A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. As digital circuits can only understand binary, inputs and outputs can assume only one of two states, 0 or 1. |
| Login | Noun or a verb. Noun: The account name used to gain access to a computer system. Not a secret (contrast with Password). Verb: the act of connecting to a computer system by giving your credentials (usually your "username" and "password") See also: Password |
| Loopback Address | The loopback address (127.0.0.1) is a pseudo IP address that always refer back to the local host and are never sent out onto a network. |
| Lossless | ossless 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. |
| 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. |
| LS | 1. Location Services. 2. UNIX command line command to list files. |
| LSI Corporation (LSI) | LSI Corporation is an electronics company based in Milpitas, California, that designs ASICs, host bus adapters, RAID adapters, storage systems, and computer networking products. |
| LUA | Limited User Account. A user account that lacks any (or all) administrative rights. cf Administrator Account (AC). It is generally recommended that a Limited User Account be used for day to day activities and an Administrator Account used only when strictly necessary. This reduces the opportunity for a system to be compromised due to the actions of the user. |
| 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. |
| LUN (Logical Unit Number) | A term used in the context of devices connected to a SCSI controller. Each device on a SCSI controller has a SCSI ID, but each SCSI ID may have several LUNs that translate to several hard disks or removable media. |
