Linux, also known as GNU/Linux, is a free and open source Unix-like computer operating system. Unlike proprietary operating systems such as Windows or Mac OS, all of Linux underlying source code is available to the general public for anyone to use, modify, and redistribute freely. Linux has gained the support of major corporations such as IBM, Sun Microsystems, Hewlett-Packard, and Novell for use in servers and is gaining popularity in the desktop market. It is used in systems ranging from supercomputers to mobile phones.

The Linux kernel is a free Unix-like operating system kernel that was created by Linus Torvalds in 1991 and subsequently improved with the assistance of developers around the world.

A Linux PC (personal computer) is usually a microcomputer that uses Linux distribution software as its operating system and application software.

Laboratory information system (LIS) is a class of software which handles storing information generated by laboratory processes. These systems often must interface with instruments and other information systems such as hospital information systems (HIS). An LIS is a highly configurable application which is customized to facilitate a wide variety of laboratory workflow models. Deciding on an LIS vendor is a major undertaking for all but the smallest labs.

Lisp programming language (LISP), originally specified in 1958, is the second-oldest (only Fortran is older) high-level programming language in widespread use. LISP has changed a great deal since its early days, and a number of dialects have existed over its history. Today, the most widely-known general-purpose Lisp dialects are Common Lisp and Scheme. Lisp was originally created as a practical mathematical notation for computer programs, based on Alonzo Church's lambda calculus. It quickly became the favored programming language for artificial intelligence research. As one of the earliest programming languages, Lisp pioneered many ideas in computer science, including tree data structures, automatic storage management, dynamic typing, object-oriented programming, and the self-hosting compiler.

Live variable analysis is performed by computer program compilers to calculate for each program point the variables that may be potentially read afterwards before their next written update.

LiveCD is an operating system distribution that is executed upon boot using a CD-ROM, without installation on a hard drive. It is one type of LiveDistro using CD-ROM as the media.

LiveDistro is a generic term for an operating system distribution that is executed upon boot, without installation on a hard drive. Typically, it is stored on bootable media such as a CD-ROM (Live CD), DVD (Live DVD), USB Flash Drive, among others.

Learning Management System (LMS) is a software package, that enables the management and delivery of learning content and resources to students. Most LMS systems are web-based to facilitate "anytime, anywhere" access to learning content and administration. At a minimum, the LMS usually allows for student registration, the delivery and tracking of e-learning courses and content, and testing, and may also allow for the management of instructor-led training classes. In the most comprehensive of LMSs, one may find tools such as competency management, skills-gap analysis, succession planning, certifications, virtual live classes, and resource allocation (venues, rooms, textbooks, instructors, etc.). Most systems allow for learners self-service, facilitating self-enrollment, and access to courses.

Loop nest optimization (LNO) is a special case of loop transformation which deals with nested loops that makes possible large reductions in the cache bandwidth necessary for some pervasive algorithms.