0L
In legal education, particularly in the United States, 0L (pronounced "zero L") is a colloquial term referring to individuals who have been accepted into law school but have not yet begun their first year of study, often during the preparatory summer period before orientation.[1] This designation parallels the standard abbreviations for enrolled students—1L for first-year, 2L for second-year, and 3L for third-year law students—and emphasizes the transitional phase between undergraduate or professional life and formal legal training.[2]
The term gained prominence as law schools recognized the need to support incoming students in acclimating to the rigors of legal analysis, reading cases, and understanding the U.S. legal system.[1] For instance, Harvard Law School launched its Zero-L online course in 2018, specifically designed for this cohort to build foundational skills through modules on topics such as case briefing, statutory interpretation, previews of 1L subjects like torts and criminal law, and the legal profession.[1][3] The program, which has enrolled tens of thousands of participants nationwide, features interactive videos, quizzes, and year-long access for a fee of $200, aiming to reduce first-year anxiety and level the playing field for students from diverse academic backgrounds.[1]
Beyond Harvard, 0L preparation has become a broader aspect of legal education, with resources including reading recommendations, workshops, and online guides to foster habits like critical reading and time management.[2] Prospective 0Ls are advised to engage in light pre-reading of landmark cases or introductory texts on legal reasoning, though over-preparation is discouraged to avoid burnout upon entering the intensive 1L curriculum.[4] This preparatory stage underscores the unique demands of law school, where success hinges on analytical skills rather than rote memorization, setting the tone for a career in law.[1]
Physics and engineering
Zeroth law of thermodynamics
The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then the two systems are in thermal equilibrium with each other.[5] This principle defines thermal equilibrium as an equivalence relation, allowing systems to be grouped into classes sharing the same temperature without direct interaction.[5]
The law was formulated by British physicist Ralph H. Fowler in the 1930s to resolve the logical sequencing of thermodynamic principles, as it underpins the concepts introduced in the first and second laws.[5] Fowler coined the term "zeroth law" while reviewing a 1935 textbook by Meghnad Saha and B.N. Srivastava, recognizing its foundational role and numbering it zero to precede the existing laws.[5] This naming reflects its status as the most basic axiom in thermodynamics, enabling the subsequent laws to build upon a consistent notion of temperature.[6]
The zeroth law establishes temperature as a fundamental, measurable property of physical systems, independent of specific measurement devices.[5] It justifies the use of thermometers by permitting indirect comparisons: a thermometer in equilibrium with one system can gauge the temperature of another via a shared reference.[7] This transitivity ensures a universal temperature scale, such as the Kelvin scale, calibrated against fixed points like the triple point of water at 273.16 K.[5]
A key illustration involves two bodies, A and B, separated from direct contact but each placed in thermal equilibrium with a third body, C (such as a thermometer).[7] Once A equilibrates with C and B equilibrates with C, no net heat flows between A and B if connected, confirming their shared temperature despite no prior interaction.[7] This example underscores the law's practical role in empirical thermometry.[5]
The zeroth law relates to the other thermodynamic laws by providing the empirical basis for temperature, upon which the first law's energy conservation and the second law's entropy principles depend.[5]
Zero-length launch
Zero-length launch is a rocketry technique developed for the rapid deployment of missiles from minimal infrastructure, in which the missile is propelled from a stationary platform using a solid-fuel booster without the need for a traditional launch rail, runway, or extended takeoff roll.[8] This method typically involves elevating the missile to a launch angle of about 15 degrees on a mobile trailer cradle before ignition.[9]
The concept emerged in the late 1940s and was refined during the 1950s by the U.S. Air Force amid Cold War demands for quick-reaction capabilities to counter potential Soviet advances.[10] Initial tests with dummy Matador missiles occurred at Holloman Air Force Base, leading to the first powered flight of a production variant on January 20, 1949, at White Sands Missile Range.[8] The system was operationalized with the Martin MGM-1 Matador cruise missile, deployed by squadrons such as the 1st Pilotless Bomber Squadron in Europe starting in 1954, enabling launches from road-accessible or sheltered sites for tactical strikes.[9]
In operation, the mechanism relies on a short-burn solid-fuel booster, such as the Thiokol unit providing 50,000 pounds of thrust for approximately 2 seconds, to accelerate the missile to a safe altitude and speed where its main turbojet engine—typically an Allison J33-A-37—ignites for sustained cruise flight.[9] The booster detaches shortly after launch, allowing the missile to follow a preset trajectory guided by radio command or later inertial systems.[8] This sequence permitted a Matador to reach flight speed in as little as 2.5 seconds, as demonstrated in public tests at Patrick Air Force Base in 1956.[10]
The primary advantages of zero-length launch included enhanced mobility and survivability, allowing deployment from unprepared or dispersed locations to evade enemy detection and enable rapid response in alert scenarios.[9] However, it was constrained to lighter payloads due to booster limitations and structural stresses on the airframe, with early variants achieving only about 400-500 miles of range.[8] By the early 1960s, the approach was largely phased out in favor of more advanced mobile transporter-erector-launchers on the successor MGM-13 Mace missile, which offered improved guidance and reduced reliance on fixed boosters.[9]
Geography and navigation
Prime meridian
The prime meridian is defined as the meridian of 0° longitude, running from the North Pole to the South Pole and passing through the Airy Transit Circle telescope at the Royal Observatory in Greenwich, London, England. This line serves as the primary reference for measuring east-west longitude on Earth, enabling standardized global navigation, mapping, and timekeeping. It was selected due to Greenwich's prominence in maritime astronomy and the widespread use of its meridian on nautical charts by the late 19th century.[11]
Historically, no single prime meridian existed universally before 1884, with countries adopting local references; France, for instance, used the Paris meridian through the Paris Observatory, located about 2°20' east of Greenwich, for official maps and time until 1911. The international standardization occurred at the International Meridian Conference in Washington, D.C., from October 1 to October 22, 1884, attended by delegates from 25 nations, which resolved by a vote of 22 to 1 (with France abstaining) to adopt the Greenwich meridian as the global zero longitude. This decision addressed inconsistencies in international shipping, telegraphy, and rail travel, promoting uniformity in positional reckoning.[12][13]
The prime meridian's significance lies in its role as the foundation for global time systems and hemispheric division. It defines Greenwich Mean Time (GMT), the solar time at 0° longitude, which was recommended as the universal time standard at the 1884 conference to facilitate synchronized worldwide operations. GMT evolved into Coordinated Universal Time (UTC), the modern atomic-based standard that maintains alignment with solar time through leap seconds, ensuring precise coordination for aviation, telecommunications, and finance. Additionally, the meridian, together with the 180° antimeridian, divides Earth into the Eastern Hemisphere (longitudes 0° to 180° east) and Western Hemisphere (0° to 180° west), providing a geopolitical and navigational boundary.[14][15][16]
In contemporary usage, the prime meridian is integral to GPS and satellite navigation systems, as well as international treaties like the United Nations Convention on the Law of the Sea, which reference it for maritime boundaries and resource delineation. While the original Greenwich line remains the conventional standard, minor discrepancies persist in specialized applications; for example, the International Earth Rotation and Reference Systems Service (IERS) defines a reference meridian approximately 102 meters east of the Airy Transit Circle to account for geophysical plate movements and precise satellite measurements. These variations are negligible for most practical purposes but highlight ongoing refinements in global geodesy.[17][18]
Longitude zero
Longitude zero, or 0° longitude, is the longitudinal line that serves as the reference point separating eastern longitudes (positive values) from western longitudes (negative values), and it physically coincides with the prime meridian. This line runs from the North Pole to the South Pole, passing through the Royal Observatory in Greenwich, London, and is fundamental to the global coordinate system used in geography.
The measurement of longitude zero is determined through precise astronomical observations, such as stellar transits, or modern satellite-based systems like GPS, which provide positional accuracy to within centimeters. Longitudes are expressed in degrees (°), minutes ('), and seconds ("), with 0° longitude divided into 60 minutes per degree and further subdivided into 60 seconds, allowing for fine-grained locational data in mapping and navigation applications.
While the Greenwich-based 0° longitude is the international standard, historical variations exist in national systems, such as the Ferro meridian (El Hierro in the Canary Islands), which served as zero longitude in older Spanish cartography and shifted longitudes eastward by approximately 17-18°. These alternative zeros were used before global standardization to align maps with local reference points.
Longitude zero has profound global impacts, forming the backbone for cartography by enabling the projection of Earth's curved surface onto flat maps, and it is critical for aviation and shipping routes that rely on standardized positioning to avoid navigational errors. Additionally, it influences the International Date Line near 180° longitude, where crossing zero longitude can affect time zone calculations and date changes in transoceanic travel.
Computing
Long integer literal
In programming languages such as C, C++, and Java, the notation 0L represents a long integer literal with the value zero, where the suffix "L" (or lowercase "l") explicitly denotes a long integer type rather than the default integer type.[19][20] This distinction ensures the literal is treated as a signed long integer, which is 64 bits wide under the LP64 data model (common on 64-bit Unix/Linux systems) but 32 bits under LLP64 (64-bit Windows), compared to the typical 32-bit int (such as Java's long, which is always 64 bits).[21]
The use of 0L is particularly valuable in arithmetic operations to promote type safety and prevent integer overflow. For instance, adding a large integer to 0L forces the computation to use long integer arithmetic throughout, avoiding truncation that could occur with default int promotion.[22][23] This is essential in scenarios involving large constants or mixed-type expressions, where implicit conversions might otherwise lead to unexpected results.
The specification for long integer literals with the "L" suffix is formalized in language standards: in C99 (ISO/IEC 9899:1999), an integer constant suffixed with "l" or "L" is of type long int if its value fits, otherwise unsigned long int; this is case-insensitive.[19] Similar rules apply in C++ (ISO/IEC 14882) and Java's Language Specification, which recommends uppercase "L" to avoid visual confusion with the digit "1".[20] In all cases, 0L directly initializes a long integer variable to zero without requiring additional casting.
Common usage appears in variable initialization and constant declarations. For example, in C or C++:
c
long x = 0L; // Initializes a long integer to zero
long x = 0L; // Initializes a long integer to zero
In Java:
java
long y = 0L; // Ensures 64-bit long type for the literal
long y = 0L; // Ensures 64-bit long type for the literal
This practice is standard for ensuring portable and predictable behavior across platforms.[22][20]
Bitwise operations with 0L
In C and C++ programming, the literal 0L represents the integer value zero with the type long int, which corresponds to a binary representation of all bits set to zero across the platform-dependent width of the long type.[24] The suffix L explicitly designates this as a long int literal, ensuring type promotion to long in expressions and avoiding unintended integer truncation or promotion during bitwise operations.[24]
Applying the unary bitwise NOT operator (~) to 0L inverts every bit, producing a value with all bits set to one. In signed long int using two's complement representation (the standard in modern C++), this yields the value -1.[25][21] For example, on a 64-bit system where long is 64 bits wide, ~0L equals 0xFFFFFFFFFFFFFFFF in hexadecimal, equivalent to -1 in decimal.[21] On 32-bit systems or platforms using the ILP32 data model, it would be 0xFFFFFFFF (still -1 signed).[21] The behavior under unsigned interpretation (e.g., casting to unsigned long) treats ~0L as the maximum value for that type, all bits one without sign extension issues.[25]
This all-ones result makes ~0L a portable idiom for generating full bit masks in bitwise operations, independent of the exact bit width of long.[26] Common applications include creating masks to set or clear flags in data structures, where ANDing with ~0L preserves all bits (identity operation) or ORing sets them entirely. In networking code, ~0L (or its unsigned counterpart ~0UL) facilitates byte-order-independent mask generation for IP address computations, such as deriving subnet masks by right-shifting (e.g., ~0UL >> (32 - prefix_length) for IPv4).[26] Similarly, in memory allocation routines, it initializes bitmaps or flags for tracking allocated blocks, ensuring complete coverage without hardcoding bit counts.[26]
Platform-specific variations arise from the size of long int and signed/unsigned semantics: under the LP64 model (common on 64-bit Unix/Linux), long is 64 bits, while LLP64 (64-bit Windows) keeps it at 32 bits, potentially affecting mask portability across architectures.[21] Programmers must consider these differences, often preferring unsigned long with ~0UL for masks to avoid sign-related shifts propagating the sign bit.[25] The C++ standard guarantees at least 32 bits for long, but exact width is implementation-defined, emphasizing the value of ~0L for adaptive, architecture-agnostic code.[21]
Education
Law school terminology
In U.S. law school culture, the term "0L" designates individuals accepted to but not yet enrolled in law school, typically those awaiting the start of their first year of study and transitioning into first-year status as "1Ls."[1][27] This slang forms part of a broader numerical progression system used to denote stages of legal education: 0L for pre-matriculation, 1L for first-year students, 2L for second-year students, and 3L for third-year students.[28][29] The "L" abbreviation universally stands for "law," reflecting the year or level within the Juris Doctor (JD) program.[30]
This terminology facilitates clear communication among law students, applicants, and professionals, particularly in discussions on admissions strategies, LSAT preparation, bar exam readiness, and early career guidance.[31][32] For instance, 0Ls often seek advice on application essays or interview techniques, distinguishing their needs from those of enrolled students focused on coursework or clerkships. The system gained traction in online law school admissions and student communities starting in the late 2000s, building on the established "1L" shorthand popularized by Scott Turow's 1977 memoir One L: The Turbulent True Story of a First Year at Harvard Law School.[33]
Unlike the undergraduate "pre-law" track, which refers to advisory coursework or majors in related fields like political science without guaranteeing law school entry, 0L specifically highlights the immediate pre-matriculation phase for accepted applicants.[27][34] Incoming 0Ls may participate in preparatory initiatives, such as Harvard Law School's Zero-L program, to ease the shift to 1L year.[1]
Harvard Zero-L Program
The Harvard Zero-L Program, often abbreviated as Zero-L or 0L, is an online preparatory course developed by Harvard Law School to equip incoming law students—referred to as 0Ls in legal education slang—with essential skills and knowledge before their first year (1L).[1] The program serves as a bridge between undergraduate studies and the rigors of legal education, focusing on foundational concepts to foster confidence and readiness.[35] It builds on the general 0L terminology used in law school communities to describe pre-enrollment students.[1]
The curriculum emphasizes practical skills such as legal reasoning, reading and briefing cases, interpreting statutes, understanding the U.S. court system, and exploring the legal profession and theory.[35] Delivered through self-paced modules featuring engaging videos, interactive exercises, and optional comprehension checks, the course typically requires 12-14 hours to complete and provides year-long access upon enrollment.[1] Additional components include previews of 1L coursework and wellness strategies for time management, designed to address common challenges like case analysis and academic adjustment.[35]
Originally piloted in summer 2018 and formally launched in 2019 for Harvard Law students, the program was created by faculty including I. Glenn Cohen to provide a shared baseline for diverse incoming classes.[3] In response to COVID-19 disruptions in 2020, Harvard expanded Zero-L nationwide, offering it for free to approximately 200,000 students at over 120 other law schools to mitigate learning gaps caused by the pandemic.[36][37] Post-pandemic, it has continued to evolve, with partnerships like those at Hofstra Law in 2020 highlighting its role in enhancing access and equity in legal education. As of recent years, Zero-L has been adopted by more than half of all U.S. law schools.[38] By 2024, the course had reached tens of thousands of learners globally.[35]
Participation in Zero-L is optional but strongly recommended for all incoming students, helping to reduce first-year stress and flatten the learning curve for those without prior legal exposure.[1] Educators and participants have noted its positive effects on building a common foundational knowledge, particularly for underrepresented groups, with over 20,000 students benefiting by easing the transition to law school demands.[35] As of 2025, the program is available for a fee of $200, though it remains a key resource for pre-law preparation.[1]
Technology
0L Network
The 0L Network is an open-source, permissionless Layer 1 blockchain protocol launched on November 16, 2021, that operates under community governance and utilizes the Move programming language for smart contract development.[39][40] It serves as a decentralized platform designed to enable scalable and secure transactions with low fees, supporting applications in decentralized finance (DeFi), non-fungible tokens (NFTs), and other smart contract-based ecosystems.[39][41]
Originating as a fork of Meta's abandoned Diem project (formerly known as Libra), the 0L Network seeks to realize the original vision of a high-throughput blockchain while prioritizing openness and accessibility, without pre-mined tokens or insider allocations.[39][40] The protocol employs a Byzantine Fault Tolerant consensus mechanism to ensure network reliability and emphasizes decentralization through user-mined token distribution via tools like the Carpe application.[39] The abbreviation "0L" derives from the project's naming as Open Libra, reflecting its roots in the Libra initiative and a stylized representation in cryptocurrency documentation.[41][40]
As of November 2025, the 0L Network (rebranded as Open Libra) continues to operate as an active blockchain, with 10 active validators, a circulating supply of approximately 763 million LIBRA tokens, and ongoing network epochs.[42][41] Its tokenomics feature a 100% freely mined supply of the native LIBRA token (also referred to as 0L in some contexts), with 80% allocated to long-term investment mechanisms such as slow wallets and sub-DAOs for specialized funding.[41][39] The network has cultivated partnerships and contributions within the broader blockchain space, including involvement from figures like Zaki Manian, a Cosmos ecosystem developer, to advance its infrastructure for DeFi and NFT applications.[39]