71-529: In computing , a linker or link editor is a computer system program that takes one or more object files (generated by a compiler or an assembler ) and combines them into a single executable file, library file, or another "object" file. A simpler version that writes its output directly to memory is called the loader , though loading is typically considered a separate process. Computer programs typically are composed of several parts or modules; these parts/modules do not need to be contained within
142-431: A monolithic whole and the ability to better define the purpose and responsibilities of each individual piece, which is essential for managing complexity and increasing long-term maintainability in software architecture . Typically, an object file can contain three kinds of symbols: For most compilers, each object file is the result of compiling one input source code file. When a program comprises multiple object files,
213-427: A shared library , the entire library has to be loaded during runtime as it is not known which functions or methods will be called during runtime. Library linking may thus be an iterative process, with some referenced modules requiring additional modules to be linked, and so on. Libraries exist for diverse purposes, and one or more system libraries are usually linked in by default. The linker also takes care of arranging
284-484: A broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents of the World Wide Web and the infrastructure to support email. Computer programming is the process of writing, testing, debugging, and maintaining the source code and documentation of computer programs. This source code
355-497: A computer's capabilities, but typically do not directly apply them in the performance of tasks that benefit the user, unlike application software. Application software, also known as an application or an app , is computer software designed to help the user perform specific tasks. Examples include enterprise software , accounting software , office suites , graphics software , and media players . Many application programs deal principally with documents . Apps may be bundled with
426-401: A few routines from a library does not require the entire library to be installed. As the compiler has no information on the layout of objects in the final output, it cannot take advantage of shorter or more efficient instructions that place a requirement on the address of another object. For example, a jump instruction can reference an absolute address or an offset from the current location, and
497-502: A larger company, these may all be separate positions within a computer support or Information Services (IS) department. In a smaller group they may be shared by a few sysadmins, or even a single person. Most employers require a bachelor's degree in a related field, such as computer science , information technology , electronics engineering , or computer engineering . Some schools also offer undergraduate degrees and graduate programs in system administration. In addition, because of
568-404: A linker (assembling object files into a program) was called loading (as in loading executable code onto a file). Additionally, in some operating systems, the same program handles both the jobs of linking and loading a program ( dynamic linking ). Many operating system environments allow dynamic linking, deferring the resolution of some undefined symbols until a program is run. That means that
639-458: A set of instructions called a computer program . The program has an executable form that the computer can use directly to execute the instructions. The same program in its human-readable source code form, enables a programmer to study and develop a sequence of steps known as an algorithm . Because the instructions can be carried out in different types of computers, a single set of source instructions converts to machine instructions according to
710-417: A single object file , and in such cases refer to each other using symbols as addresses into other modules, which are mapped into memory addresses when linked for execution. While the process of linking is meant to ultimately combine these independent parts, there are many good reasons to develop those separately at the source -level. Among these reasons are the ease of organizing several smaller pieces over
781-473: A software project. A linker script may be passed to GNU ld to exercise greater control over the linking process. The GNU linker is part of the GNU Binary Utilities (binutils). Two versions of ld are provided in binutils: the traditional GNU ld based on bfd , and a "streamlined" ELF-only version called gold . The command-line and linker script syntaxes of GNU ld is the de facto standard in much of
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#1732868670097852-435: A superposition, i.e. in both states of one and zero, simultaneously. Thus, the value of the qubit is not between 1 and 0, but changes depending on when it is measured. This trait of qubits is known as quantum entanglement , and is the core idea of quantum computing that allows quantum computers to do large scale computations. Quantum computing is often used for scientific research in cases where traditional computers do not have
923-421: Is spintronics . Spintronics can provide computing power and storage, without heat buildup. Some research is being done on hybrid chips, which combine photonics and spintronics. There is also research ongoing on combining plasmonics , photonics, and electronics. Cloud computing is a model that allows for the use of computing resources, such as servers or applications, without the need for interaction between
994-460: Is a discipline that integrates several fields of electrical engineering and computer science required to develop computer hardware and software. Computer engineers usually have training in electronic engineering (or electrical engineering ), software design , and hardware-software integration, rather than just software engineering or electronic engineering. Computer engineers are involved in many hardware and software aspects of computing, from
1065-414: Is a person who writes computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist who writes code for many kinds of software. One who practices or professes a formal approach to programming may also be known as a programmer analyst. A programmer's primary computer language ( C , C++ , Java , Lisp , Python , etc.) is often prefixed to
1136-421: Is a separate role responsible for overall security and the upkeep of firewalls and intrusion detection systems , but all sysadmins are generally responsible for the security of computer systems. A system administrator's responsibilities might include: In larger organizations, some of the tasks above may be divided among different system administrators or members of different organizational groups. For example,
1207-409: Is also synonymous with counting and calculating . In earlier times, it was used in reference to the action performed by mechanical computing machines , and before that, to human computers . The history of computing is longer than the history of computing hardware and includes the history of methods intended for pen and paper (or for chalk and slate) with or without the aid of tables. Computing
1278-414: Is an area of research that brings together the disciplines of computer science, information theory, and quantum physics. While the idea of information as part of physics is relatively new, there appears to be a strong tie between information theory and quantum mechanics. Whereas traditional computing operates on a binary system of ones and zeros, quantum computing uses qubits . Qubits are capable of being in
1349-423: Is computer software designed to operate and control computer hardware, and to provide a platform for running application software. System software includes operating systems , utility software , device drivers , window systems , and firmware . Frequently used development tools such as compilers , linkers , and debuggers are classified as system software. System software and middleware manage and integrate
1420-476: Is denoted CMOS-integrated nanophotonics (CINP). One benefit of optical interconnects is that motherboards, which formerly required a certain kind of system on a chip (SoC), can now move formerly dedicated memory and network controllers off the motherboards, spreading the controllers out onto the rack. This allows standardization of backplane interconnects and motherboards for multiple types of SoCs, which allows more timely upgrades of CPUs. Another field of research
1491-417: Is finally loaded into memory (just before execution). This pass is usually omitted on hardware offering virtual memory : every program is put into its own address space, so there is no conflict even if all programs load at the same base address. This pass may also be omitted if the executable is a position independent executable. On some Unix variants, such as SINTRAN III , the process performed by
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#17328686700971562-468: Is in the form and format of 80-byte punched-card images, so that updates can be introduced into a system using that medium. In later releases of OS/360 and in subsequent systems, load-modules contain additional data about versions of components modules, to create a traceable record of updates. It also allows one to add, change, or remove an overlay structure from an already linked load module. The term "linkage editor" should not be construed as implying that
1633-485: Is intimately tied to the representation of numbers, though mathematical concepts necessary for computing existed before numeral systems . The earliest known tool for use in computation is the abacus , and it is thought to have been invented in Babylon circa between 2700 and 2300 BC. Abaci, of a more modern design, are still used as calculation tools today. The first recorded proposal for using digital electronics in computing
1704-710: Is its potential to support energy efficiency. Allowing thousands of instances of computation to occur on one single machine instead of thousands of individual machines could help save energy. It could also ease the transition to renewable energy source, since it would suffice to power one server farm with renewable energy, rather than millions of homes and offices. However, this centralized computing model poses several challenges, especially in security and privacy. Current legislation does not sufficiently protect users from companies mishandling their data on company servers. This suggests potential for further legislative regulations on cloud computing and tech companies. Quantum computing
1775-559: Is sometimes considered a sub-discipline of electrical engineering , telecommunications, computer science , information technology, or computer engineering , since it relies upon the theoretical and practical application of these disciplines. The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users. This includes millions of private, public, academic, business, and government networks, ranging in scope from local to global. These networks are linked by
1846-687: Is the application of computers and telecommunications equipment to store, retrieve, transmit, and manipulate data, often in the context of a business or other enterprise. The term is commonly used as a synonym for computers and computer networks, but also encompasses other information distribution technologies such as television and telephones. Several industries are associated with information technology, including computer hardware, software, electronics , semiconductors , internet, telecom equipment , e-commerce , and computer services . DNA-based computing and quantum computing are areas of active research for both computing hardware and software, such as
1917-463: Is the result of the linker copying all library routines used in the program into the executable image. This may require more disk space and memory than dynamic linking, but is more portable, since it does not require the presence of the library on the system where it runs. Static linking also prevents "DLL hell", since each program includes exactly the versions of library routines that it requires, with no conflict with other programs. A program using just
1988-509: Is the study of complementary networks of hardware and software (see information technology) that people and organizations use to collect, filter, process, create, and distribute data . The ACM 's Computing Careers describes IS as: "A majority of IS [degree] programs are located in business schools; however, they may have different names such as management information systems, computer information systems, or business information systems. All IS degrees combine business and computing topics, but
2059-449: Is thus often developed by a team of domain experts, each a specialist in some area of development. However, the term programmer may apply to a range of program quality, from hacker to open source contributor to professional. It is also possible for a single programmer to do most or all of the computer programming needed to generate the proof of concept to launch a new killer application . A programmer, computer programmer, or coder
2130-429: Is written in a programming language , which is an artificial language that is often more restrictive than natural languages , but easily translated by the computer. Programming is used to invoke some desired behavior (customization) from the machine. Writing high-quality source code requires knowledge of both the computer science domain and the domain in which the application will be used. The highest-quality software
2201-554: The CPU type. The execution process carries out the instructions in a computer program. Instructions express the computations performed by the computer. They trigger sequences of simple actions on the executing machine. Those actions produce effects according to the semantics of the instructions. Computer hardware includes the physical parts of a computer, including the central processing unit , memory , and input/output . Computational logic and computer architecture are key topics in
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2272-506: The Unix-like world. The LLVM project's linker, lld , is designed to be drop-in compatible, and may be used directly with the GNU compiler. Another drop-in replacement, mold, is a highly parallelized and faster alternative which is also supported by GNU tools. Computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery . It includes
2343-444: The function of the program it implements, either by directly providing instructions to the computer hardware or by serving as input to another piece of software. The term was coined to contrast with the old term hardware (meaning physical devices). In contrast to hardware, software is intangible. Software is also sometimes used in a more narrow sense, meaning application software only. System software, or systems software,
2414-506: The linker relaxation pass subsequently reassigns addresses, which may in turn allow more potential relaxations to occur. In general, the substituted sequences are shorter, which allows this process to always converge on the best solution given a fixed order of objects; if this is not the case, relaxations can conflict, and the linker needs to weigh the advantages of either option. While instruction relaxation typically occurs at link-time, inner-module relaxation can already take place as part of
2485-880: The above titles, and those who work in a web environment often prefix their titles with Web . The term programmer can be used to refer to a software developer , software engineer, computer scientist , or software analyst . However, members of these professions typically possess other software engineering skills, beyond programming. The computer industry is made up of businesses involved in developing computer software, designing computer hardware and computer networking infrastructures, manufacturing computer components, and providing information technology services, including system administration and maintenance. The software industry includes businesses engaged in development , maintenance , and publication of software. The industry also includes software services , such as training , documentation , and consulting. Computer engineering
2556-423: The additional capability of allowing the addition, replacement, and/or deletion of individual program sections. Operating systems such as OS/360 have format for executable load-modules containing supplementary data about the component sections of a program, so that an individual program section can be replaced, and other parts of the program updated so that relocatable addresses and other references can be corrected by
2627-421: The behavior of software in order to deploy it and to troubleshoot problems, and generally know several programming languages used for scripting or automation of routine tasks. A typical sysadmin's role is not to design or write new application software but when they are responsible for automating system or application configuration with various configuration management tools, the lines somewhat blur. Depending on
2698-457: The challenges in implementing computations. For example, programming language theory studies approaches to the description of computations, while the study of computer programming investigates the use of programming languages and complex systems . The field of human–computer interaction focuses on the challenges in making computers and computations useful, usable, and universally accessible to humans. The field of cybersecurity pertains to
2769-560: The computer and its system software, or may be published separately. Some users are satisfied with the bundled apps and need never install additional applications. The system software manages the hardware and serves the application, which in turn serves the user. Application software applies the power of a particular computing platform or system software to a particular purpose. Some apps, such as Microsoft Office , are developed in multiple versions for several different platforms; others have narrower requirements and are generally referred to by
2840-417: The computing power to do the necessary calculations, such in molecular modeling . Large molecules and their reactions are far too complex for traditional computers to calculate, but the computational power of quantum computers could provide a tool to perform such calculations. System administrator An IT administrator , system administrator , sysadmin , or admin is a person who is responsible for
2911-448: The design of individual microprocessors , personal computers, and supercomputers , to circuit design . This field of engineering includes not only the design of hardware within its own domain, but also the interactions between hardware and the context in which it operates. Software engineering is the application of a systematic, disciplined, and quantifiable approach to the design, development, operation, and maintenance of software, and
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2982-414: The development of quantum algorithms . Potential infrastructure for future technologies includes DNA origami on photolithography and quantum antennae for transferring information between ion traps. By 2011, researchers had entangled 14 qubits . Fast digital circuits , including those based on Josephson junctions and rapid single flux quantum technology, are becoming more nearly realizable with
3053-437: The discovery of nanoscale superconductors . Fiber-optic and photonic (optical) devices, which already have been used to transport data over long distances, are starting to be used by data centers, along with CPU and semiconductor memory components. This allows the separation of RAM from CPU by optical interconnects. IBM has created an integrated circuit with both electronic and optical information processing in one chip. This
3124-686: The emphasis between technical and organizational issues varies among programs. For example, programs differ substantially in the amount of programming required." The study of IS bridges business and computer science , using the theoretical foundations of information and computation to study various business models and related algorithmic processes within a computer science discipline. The field of Computer Information Systems (CIS) studies computers and algorithmic processes, including their principles, their software and hardware designs, their applications, and their impact on society while IS emphasizes functionality over design. Information technology (IT)
3195-644: The engineering paradigm. The generally accepted concepts of Software Engineering as an engineering discipline have been specified in the Guide to the Software Engineering Body of Knowledge (SWEBOK). The SWEBOK has become an internationally accepted standard in ISO/IEC TR 19759:2015. Computer science or computing science (abbreviated CS or Comp Sci) is the scientific and practical approach to computation and its applications. A computer scientist specializes in
3266-449: The executable code still contains undefined symbols, plus a list of objects or libraries that will provide definitions for these. Loading the program will load these objects/libraries as well, and perform a final linking. This approach offers two advantages: There are also disadvantages: Contained or virtual environments may further allow system administrators to mitigate or trade-off these individual pros and cons. Static linking
3337-434: The field of computer hardware. Computer software, or just software , is a collection of computer programs and related data, which provides instructions to a computer. Software refers to one or more computer programs and data held in the storage of the computer. It is a set of programs, procedures, algorithms, as well as its documentation concerned with the operation of a data processing system. Program software performs
3408-442: The first silicon dioxide field effect transistors at Bell Labs, the first transistors in which drain and source were adjacent at the surface. Subsequently, a team demonstrated a working MOSFET at Bell Labs 1960. The MOSFET made it possible to build high-density integrated circuits , leading to what is known as the computer revolution or microcomputer revolution . A computer is a machine that manipulates data according to
3479-511: The first working transistor , the point-contact transistor , in 1947. In 1953, the University of Manchester built the first transistorized computer , the Manchester Baby . However, early junction transistors were relatively bulky devices that were difficult to mass-produce, which limited them to a number of specialised applications. In 1957, Frosch and Derick were able to manufacture
3550-427: The linkage editor, as part of the process. One advantage of this is that it allows a program to be maintained without having to keep all of the intermediate object files, or without having to re-compile program sections that haven't changed. It also permits program updates to be distributed in the form of small files (originally card decks ), containing only the object module to be replaced. In such systems, object code
3621-430: The linker combines these files into a unified executable program, resolving the symbols as it goes along. Linkers can take objects from a collection called a library or runtime library . Most linkers do not include all the object files in a static library in the output executable; they include only those object files from the library that are referenced by other object files or libraries directly or indirectly. But for
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#17328686700973692-542: The linker is known as "ld". Origins of the name "ld" are "LoaDer" and "Link eDitor". The term "loader" was used to describe the process of loading external symbols from other programs during the process of linking. The GNU linker (or GNU ld) is the GNU Project 's free software implementation of the Unix command ld. GNU ld runs the linker, which creates an executable file (or a library) from object files created during compilation of
3763-420: The objects in a program's address space . This may involve relocating code that assumes a specific base address into another base. Since a compiler seldom knows where an object will reside, it often assumes a fixed base location (for example, zero ). Relocating machine code may involve re-targeting absolute jumps, loads, and stores. The executable output by the linker may need another relocation pass when it
3834-525: The offset could be expressed with different lengths depending on the distance to the target. By first generating the most conservative instruction (usually the largest relative or absolute variant, depending on platform) and adding relaxation hints , it is possible to substitute shorter or more efficient instructions during the final link. In regard to jump optimizations this is also called automatic jump-sizing . This step can be performed only after all input objects have been read and assigned temporary addresses;
3905-407: The optimizing process at compile-time . In some cases, relaxation can also occur at load-time as part of the relocation process or combined with dynamic dead-code elimination techniques. In IBM System/360 mainframe environments such as OS/360 , including z/OS for the z/Architecture mainframes, this type of program is known as a linkage editor . As the name implies a linkage editor has
3976-499: The organization use the computers. Perhaps the most important skill for a system administrator is problem solving —frequently under various sorts of constraints and stress. The sysadmin is on call when a computer system goes down or malfunctions, and must be able to quickly and correctly diagnose what is wrong and how best to fix it. They may also need to have teamwork and communication skills; as well as being able to install and configure hardware and software. Sysadmins must understand
4047-460: The owner of these resources and the end user. It is typically offered as a service, making it an example of Software as a Service , Platforms as a Service , and Infrastructure as a Service , depending on the functionality offered. Key characteristics include on-demand access, broad network access, and the capability of rapid scaling. It allows individual users or small business to benefit from economies of scale . One area of interest in this field
4118-480: The platform they run on. For example, a geography application for Windows or an Android application for education or Linux gaming . Applications that run only on one platform and increase the desirability of that platform due to the popularity of the application, known as killer applications . A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow
4189-762: The practical nature of system administration and the easy availability of open-source server software, many system administrators enter the field self-taught. Generally, a prospective employee will be required to have experience with the computer systems they are expected to manage. In most cases, candidates are expected to possess industry certifications such as the Microsoft MCSA , MCSE , MCITP , Red Hat RHCE , Novell CNA , CNE , Cisco CCNA or CompTIA 's A+ or Network+ , Sun Certified SCNA , Linux Professional Institute , Linux Foundation Certified Engineer or Linux Foundation Certified System Administrator, among others. Sometimes, almost exclusively in smaller sites,
4260-414: The program operates in a user-interactive mode like a text editor. It is intended for batch-mode execution, with the editing commands being supplied by the user in sequentially organized files, such as punched cards , DASD , or magnetic tape . Linkage editing ( IBM nomenclature) or consolidation or collection ( ICL nomenclature) refers to the linkage editor's or consolidator's act of combining
4331-522: The protection of computer systems and networks. This includes information and data privacy , preventing disruption of IT services and prevention of theft of and damage to hardware, software, and data. Data science is a field that uses scientific and computing tools to extract information and insights from data, driven by the increasing volume and availability of data. Data mining , big data , statistics, machine learning and deep learning are all interwoven with data science. Information systems (IS)
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#17328686700974402-411: The role of system administrator may be given to a skilled user in addition to or in replacement of their duties. The subject matter of system administration includes computer systems and the ways people use them in an organization. This entails a knowledge of operating systems and applications , as well as hardware and software troubleshooting , but also knowledge of the purposes for which people in
4473-596: The rules and data formats for exchanging information in a computer network, and provide the basis for network programming . One well-known communications protocol is Ethernet , a hardware and link layer standard that is ubiquitous in local area networks . Another common protocol is the Internet Protocol Suite , which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, host-to-host data transfer, and application-specific data transmission formats. Computer networking
4544-454: The sharing of resources and information. When at least one process in one device is able to send or receive data to or from at least one process residing in a remote device, the two devices are said to be in a network. Networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, scale, topology , and organizational scope. Communications protocols define
4615-411: The study and experimentation of algorithmic processes, and the development of both hardware and software. Computing has scientific, engineering, mathematical, technological, and social aspects. Major computing disciplines include computer engineering , computer science , cybersecurity , data science , information systems , information technology , and software engineering . The term computing
4686-442: The study of these approaches. That is, the application of engineering to software. It is the act of using insights to conceive, model and scale a solution to a problem. The first reference to the term is the 1968 NATO Software Engineering Conference , and was intended to provoke thought regarding the perceived software crisis at the time. Software development , a widely used and more generic term, does not necessarily subsume
4757-566: The sysadmin's role and skillset they may be expected to understand equivalent key/core concepts a software engineer understands. That said, system administrators are not software engineers or developers , in the job title sense. Particularly when dealing with Internet -facing or business-critical systems, a sysadmin must have a strong grasp of computer security . This includes not merely deploying software patches, but also preventing break-ins and other security problems with preventive measures. In some organizations, computer security administration
4828-446: The theory of computation and the design of computational systems. Its subfields can be divided into practical techniques for its implementation and application in computer systems , and purely theoretical areas. Some, such as computational complexity theory , which studies fundamental properties of computational problems , are highly abstract, while others, such as computer graphics , emphasize real-world applications. Others focus on
4899-670: The upkeep, configuration, and reliable operation of computer systems , especially multi-user computers, such as servers . The system administrator seeks to ensure that the uptime , performance , resources , and security of the computers they manage meet the needs of the users , without exceeding a set budget when doing so. To meet these needs, a system administrator may acquire, install, or upgrade computer components and software ; provide routine automation; maintain security policies; troubleshoot ; train or supervise staff; or offer technical support for projects. Many organizations staff offer jobs related to system administration. In
4970-608: The various pieces into a relocatable binary, whereas the loading and relocation into an absolute binary at the target address is normally considered a separate step. In the beginning linkers gave users very limited control over the arrangement of generated output object files. As the target systems became complex with different memory requirements such as embedded systems, it became necessary to give users control to generate output object files with their specific requirements such as defining base addresses' of segments. Linkers control scripts were used for this. On Unix and Unix-like systems,
5041-488: Was the 1931 paper "The Use of Thyratrons for High Speed Automatic Counting of Physical Phenomena" by C. E. Wynn-Williams . Claude Shannon 's 1938 paper " A Symbolic Analysis of Relay and Switching Circuits " then introduced the idea of using electronics for Boolean algebraic operations. The concept of a field-effect transistor was proposed by Julius Edgar Lilienfeld in 1925. John Bardeen and Walter Brattain , while working under William Shockley at Bell Labs , built
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