Computer programming is the process of performing a particular
computation
Computation is any type of arithmetic or non-arithmetic calculation that follows a well-defined model (e.g., an algorithm).
Mechanical or electronic devices (or, historically, people) that perform computations are known as ''computers''. An es ...
(or more generally, accomplishing a specific
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, e ...
result), usually by designing and building an
executable
In computing, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instruction (computer science), instructi ...
computer program
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components.
A computer program ...
. Programming involves tasks such as analysis, generating
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...
s,
profiling algorithms' accuracy and resource consumption, and the implementation of algorithms (usually in a chosen
programming language
A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language.
The description of a programming ...
, commonly referred to as coding). The
source code
In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...
of a program is written in one or more languages that are intelligible to
programmer
A computer programmer, sometimes referred to as a software developer, a software engineer, a programmer or a coder, is a person who creates computer programs — often for larger computer software.
A programmer is someone who writes/creates ...
s, rather than
machine code
In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very ...
, which is directly executed by the
central processing unit
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...
. The purpose of programming is to find a sequence of instructions that will automate the performance of a task (which can be as complex as an
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
) on a
computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
, often for solving a given problem. Proficient programming thus usually requires expertise in several different subjects, including knowledge of the
application domain
An application domain is a mechanism (similar to a process in an operating system) used within the Common Language Infrastructure (CLI) to isolate executed software applications from one another so that they do not affect each other. Each applicati ...
, specialized algorithms, and formal
logic
Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from premises ...
.
Tasks accompanying and related to programming include
testing
An examination (exam or evaluation) or test is an educational assessment intended to measure a test-taker's knowledge, skill, aptitude, physical fitness, or classification in many other topics (e.g., beliefs). A test may be administered verba ...
,
debugging
In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems.
Debugging tactics can involve in ...
,
source code
In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...
maintenance, implementation of
build systems, and management of derived
artifacts, such as the
machine code
In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very ...
of
computer programs
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components.
A computer program i ...
. These might be considered part of the programming process, but often the term ''
software development
Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development invol ...
'' is used for this larger process with the term ''programming'', ''implementation'', or ''coding'' reserved for the actual writing of code. ''
Software engineering
Software engineering is a systematic engineering approach to software development.
A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term '' ...
'' combines
engineering
Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...
techniques with
software development
Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development invol ...
practices. ''
Reverse engineering
Reverse engineering (also known as backwards engineering or back engineering) is a process or method through which one attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accompli ...
'' is a related process used by designers, analysts, and programmers to understand an existing program and re-implement its function.
History
Programmable devices have existed for centuries. As early as the 9th century, a programmable
music sequencer
A music sequencer (or audio sequencer or simply sequencer) is a device or application software that can record, edit, or play back music, by handling note and performance information in several forms, typically CV/Gate, MIDI, or Open Sound Cont ...
was invented by the Persian
Banu Musa
Banu or BANU may refer to:
* Banu (name)
* Banu (Arabic), Arabic word for "the sons of" or "children of"
* Banu (makeup artist), an Indian makeup artist
* Banu Chichek, a character in the ''Book of Dede Korkut''
* Bulgarian Agrarian National Union ...
brothers, who described an automated mechanical
flute
The flute is a family of classical music instrument in the woodwind group. Like all woodwinds, flutes are aerophones, meaning they make sound by vibrating a column of air. However, unlike woodwind instruments with reeds, a flute is a reedless ...
player in the ''
Book of Ingenious Devices
The ''Book of Ingenious Devices'' (Arabic: كتاب الحيل ''Kitab al-Hiyal'', Persian: كتاب ترفندها ''Ketab tarfandha'', literally: "The Book of Tricks") is a large illustrated work on mechanical devices, including automata, publi ...
''.
In 1206, the Arab engineer
Al-Jazari
Badīʿ az-Zaman Abu l-ʿIzz ibn Ismāʿīl ibn ar-Razāz al-Jazarī (1136–1206, ar, بديع الزمان أَبُ اَلْعِزِ إبْنُ إسْماعِيلِ إبْنُ الرِّزاز الجزري, ) was a polymath: a scholar, ...
invented a programmable
drum machine where a musical mechanical
automaton
An automaton (; plural: automata or automatons) is a relatively self-operating machine, or control mechanism designed to automatically follow a sequence of operations, or respond to predetermined instructions.Automaton – Definition and More ...
could be made to play different rhythms and drum patterns, via pegs and
cam
Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bind ...
s.
Noel Sharkey
Noel Sharkey (born 14 December 1948) is a computer scientist born in Belfast, Northern Ireland. He is best known to the British public for his appearances on television as an expert on robotics; including the BBC Two television series '' Robot ...
(2007)
A 13th Century Programmable Robot
University of Sheffield
, mottoeng = To discover the causes of things
, established = – University of SheffieldPredecessor institutions:
– Sheffield Medical School – Firth College – Sheffield Technical School – University College of Sheffield
, type = Pu ...
In 1801, the
Jacquard loom
The Jacquard machine () is a device fitted to a loom that simplifies the process of manufacturing textiles with such complex patterns as brocade, damask and matelassé. The resulting ensemble of the loom and Jacquard machine is then called a Ja ...
could produce entirely different weaves by changing the "program" – a series of
pasteboard
Card stock, also called cover stock and pasteboard, is paper that is thicker and more durable than normal writing and printing paper, but thinner and more flexible than other forms of paperboard.
Card stock is often used for business cards, p ...
cards with holes punched in them.
Code-breaking
Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic sec ...
algorithms have also existed for centuries. In the 9th century, the
Arab mathematician Al-Kindi
Abū Yūsuf Yaʻqūb ibn ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī (; ar, أبو يوسف يعقوب بن إسحاق الصبّاح الكندي; la, Alkindus; c. 801–873 AD) was an Arab Muslim philosopher, polymath, mathematician, physician ...
described a
cryptographic
Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adve ...
algorithm for deciphering encrypted code, in ''A Manuscript on Deciphering Cryptographic Messages''. He gave the first description of
cryptanalysis
Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic sec ...
by
frequency analysis
In cryptanalysis, frequency analysis (also known as counting letters) is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers.
Frequency analysis is based on t ...
, the earliest code-breaking algorithm.
The first
computer program
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components.
A computer program ...
is generally dated to 1843, when mathematician
Ada Lovelace
Augusta Ada King, Countess of Lovelace (''née'' Byron; 10 December 1815 – 27 November 1852) was an English mathematician and writer, chiefly known for her work on Charles Babbage's proposed mechanical general-purpose computer, the A ...
published an
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...
to calculate a sequence of
Bernoulli numbers
In mathematics, the Bernoulli numbers are a sequence of rational numbers which occur frequently in analysis. The Bernoulli numbers appear in (and can be defined by) the Taylor series expansions of the tangent and hyperbolic tangent functions, ...
, intended to be carried out by
Charles Babbage
Charles Babbage (; 26 December 1791 – 18 October 1871) was an English polymath. A mathematician, philosopher, inventor and mechanical engineer, Babbage originated the concept of a digital programmable computer.
Babbage is considered ...
's
Analytical Engine
The Analytical Engine was a proposed mechanical general-purpose computer designed by English mathematician and computer pioneer Charles Babbage. It was first described in 1837 as the successor to Babbage's difference engine, which was a des ...
.
![PunchCardDecks](https://upload.wikimedia.org/wikipedia/commons/8/86/PunchCardDecks.agr.jpg)
In the 1880s
Herman Hollerith
Herman Hollerith (February 29, 1860 – November 17, 1929) was a German-American statistician, inventor, and businessman who developed an electromechanical tabulating machine
The tabulating machine was an electromechanical machine designed t ...
invented the concept of storing ''data'' in machine-readable form. Later a
control panel (plug board) added to his 1906 Type I Tabulator allowed it to be programmed for different jobs, and by the late 1940s,
unit record equipment
Starting at the end of the nineteenth century, well before the advent of electronic computers, data processing was performed using electromechanical machines collectively referred to as unit record equipment, electric accounting machines (EAM) o ...
such as the
IBM 602
The IBM 602 Calculating Punch, introduced in 1946, was an electromechanical calculator capable of addition, subtraction, multiplication, and division. The 602 was IBM's first machine that did division. (The IBM 601, introduced in 1931, only multip ...
and
IBM 604
The IBM 604 Electronic Calculating Punch was the world's first mass-produced electronic calculator along with its predecessor the IBM 603. , were programmed by control panels in a similar way, as were the first
electronic computer
A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These progra ...
s. However, with the concept of the
stored-program computer
A stored-program computer is a computer that stores program instructions in electronically or optically accessible memory. This contrasts with systems that stored the program instructions with plugboards or similar mechanisms.
The definition i ...
introduced in 1949, both programs and data were stored and manipulated in the same way in
computer memory
In computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices. The term ''memory'' is often synonymous with the term ''primary storage ...
.
Machine language
Machine code
In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very ...
was the language of early programs, written in the
instruction set
In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...
of the particular machine, often in
binary
Binary may refer to:
Science and technology Mathematics
* Binary number, a representation of numbers using only two digits (0 and 1)
* Binary function, a function that takes two arguments
* Binary operation, a mathematical operation that t ...
notation.
Assembly language
In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence be ...
s were soon developed that let the programmer specify instruction in a text format (e.g., ADD X, TOTAL), with abbreviations for each operation code and meaningful names for specifying addresses. However, because an assembly language is little more than a different notation for a machine language, two machines with
different instruction sets also have different assembly languages.
Compiler languages
High-level language
In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ''elements'', be easier to us ...
s made the process of developing a program simpler and more understandable, and less bound to the underlying
hardware.
The first compiler related tool, the
A-0 System, was developed in 1952 by
Grace Hopper
Grace Brewster Hopper (; December 9, 1906 – January 1, 1992) was an American computer scientist, mathematician, and United States Navy Rear admiral (United States), rear admiral. One of the first programmers of the Harvard Mark I, Harvard Mar ...
, who also coined the term 'compiler'.
Maurice V. Wilkes
Sir Maurice Vincent Wilkes (26 June 1913 – 29 November 2010) was a British computer scientist who designed and helped build the Electronic Delay Storage Automatic Calculator (EDSAC), one of the earliest stored program computers, and who in ...
. 1968. Computers Then and Now. Journal of the Association for Computing Machinery, 15(1):1–7, January. p. 3 (a comment in brackets added by editor), "(I do not think that the term compiler was then 953
Year 953 ( CMLIII) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.
Events
By place
Byzantine Empire
* Battle of Marash: Emir Sayf al-Dawla marches north into the Byzantine Empire an ...
in general use, although it had in fact been introduced by Grace Hopper.)"
The World's First COBOL Compilers FORTRAN, the first widely used high-level language to have a functional implementation, came out in 1957,
and many other languages were soon developed—in particular,
COBOL
COBOL (; an acronym for "common business-oriented language") is a compiled English-like computer programming language designed for business use. It is an imperative, procedural and, since 2002, object-oriented language. COBOL is primarily us ...
aimed at commercial data processing, and
Lisp
A lisp is a speech impairment in which a person misarticulates sibilants (, , , , , , , ). These misarticulations often result in unclear speech.
Types
* A frontal lisp occurs when the tongue is placed anterior to the target. Interdental lisping ...
for computer research.
These compiled languages allow the programmer to write programs in terms that are syntactically richer, and more capable of
abstracting
An abstract is a brief summary of a research article, thesis, review, conference proceeding, or any in-depth analysis of a particular subject and is often used to help the reader quickly ascertain the paper's purpose. When used, an abstract always ...
the code, making it easy to target for varying machine instruction sets via compilation declarations and heuristics. Compilers harnessed the power of computers to make programming easier
[ by allowing programmers to specify calculations by entering a formula using ]infix notation
Infix notation is the notation commonly used in arithmetical and logical formulae and statements. It is characterized by the placement of operators between operands—" infixed operators"—such as the plus sign in .
Usage
Binary relations a ...
.
Source code entry
Programs were mostly entered using punched cards or paper tape
Five- and eight-hole punched paper tape
Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop
Punched tape or perforated paper tape is a form of data storage ...
. By the late 1960s, data storage device
Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are conside ...
s and computer terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and ...
s became inexpensive enough that programs could be created by typing directly into the computers. Text editor
A text editor is a type of computer program that edits plain text. Such programs are sometimes known as "notepad" software (e.g. Windows Notepad). Text editors are provided with operating systems and software development packages, and can be us ...
s were also developed that allowed changes and corrections to be made much more easily than with punched cards
A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to d ...
.
Modern programming
Quality requirements
Whatever the approach to development may be, the final program must satisfy some fundamental properties. The following properties are among the most important:
*Reliability
Reliability, reliable, or unreliable may refer to:
Science, technology, and mathematics Computing
* Data reliability (disambiguation), a property of some disk arrays in computer storage
* High availability
* Reliability (computer networking), a ...
: how often the results of a program are correct. This depends on conceptual correctness of algorithms and minimization of programming mistakes, such as mistakes in resource management (e.g., buffer overflow
In information security and programming, a buffer overflow, or buffer overrun, is an anomaly whereby a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory locations.
Buffers are areas of memory ...
s and race condition
A race condition or race hazard is the condition of an electronics, software, or other system where the system's substantive behavior is dependent on the sequence or timing of other uncontrollable events. It becomes a bug when one or more of t ...
s) and logic errors (such as division by zero or off-by-one error
An off-by-one error or off-by-one bug (known by acronyms OBOE, OBO, OB1 and OBOB) is a logic error involving the discrete equivalent of a boundary condition. It often occurs in computer programming when an iterative loop iterates one time too m ...
s).
*Robustness
Robustness is the property of being strong and healthy in constitution. When it is transposed into a system, it refers to the ability of tolerating perturbations that might affect the system’s functional body. In the same line ''robustness'' ca ...
: how well a program anticipates problems due to errors (not bugs). This includes situations such as incorrect, inappropriate or corrupt data, unavailability of needed resources such as memory, operating system services, and network connections, user error, and unexpected power outages.
*Usability
Usability can be described as the capacity of a system to provide a condition for its users to perform the tasks safely, effectively, and efficiently while enjoying the experience. In software engineering, usability is the degree to which a soft ...
: the ergonomics
Human factors and ergonomics (commonly referred to as human factors) is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Four primary goals of human factors learnin ...
of a program: the ease with which a person can use the program for its intended purpose or in some cases even unanticipated purposes. Such issues can make or break its success even regardless of other issues. This involves a wide range of textual, graphical, and sometimes hardware elements that improve the clarity, intuitiveness, cohesiveness and completeness of a program's user interface.
* Portability: the range of computer hardware
Computer hardware includes the physical parts of a computer, such as the computer case, case, central processing unit (CPU), Random-access memory, random access memory (RAM), Computer monitor, monitor, Computer mouse, mouse, Computer keyboard, ...
and operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
platforms on which the source code of a program can be compiled
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...
/ interpreted and run. This depends on differences in the programming facilities provided by the different platforms, including hardware and operating system resources, expected behavior of the hardware and operating system, and availability of platform-specific compilers (and sometimes libraries) for the language of the source code.
*Maintainability
In engineering, maintainability is the ease with which a product can be maintained to:
* correct defects or their cause,
* Repair or replace faulty or worn-out components without having to replace still working parts,
* prevent unexpected working ...
: the ease with which a program can be modified by its present or future developers in order to make improvements or to customize, fix bugs and security holes, or adapt it to new environments. Good practices during initial development make the difference in this regard. This quality may not be directly apparent to the end user but it can significantly affect the fate of a program over the long term.
*Efficiency
Efficiency is the often measurable ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without ...
/performance
A performance is an act of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function.
Management science
In the work place ...
: Measure of system resources a program consumes (processor time, memory space, slow devices such as disks, network bandwidth and to some extent even user interaction): the less, the better. This also includes careful management of resources, for example cleaning up temporary file
A temporary file is a file created to store information temporarily, either for a program's intermediate use or for transfer to a permanent file when complete. It may be created by computer programs for a variety of purposes, such as when a program ...
s and eliminating memory leak
In computer science, a memory leak is a type of resource leak that occurs when a computer program incorrectly manages memory allocations in a way that Computer memory, memory which is no longer needed is not released. A memory leak may also happe ...
s. This is often discussed under the shadow of a chosen programming language. Although the language certainly affects performance, even slower languages, such as Python
Python may refer to:
Snakes
* Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia
** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia
* Python (mythology), a mythical serpent
Computing
* Python (pro ...
, can execute programs instantly from a human perspective. Speed, resource usage, and performance are important for programs that bottleneck
Bottleneck literally refers to the narrowed portion (neck) of a bottle
A bottle is a narrow-necked container made of an impermeable material (such as glass, plastic or aluminium) in various shapes and sizes that stores and transports liquids ...
the system, but efficient use of programmer time is also important and is related to cost: more hardware may be cheaper.
Readability of source code
In computer programming, readability
Readability is the ease with which a reader can understand a written text. In natural language, the readability of text depends on its content (the complexity of its vocabulary and syntax) and its presentation (such as typographic aspects that a ...
refers to the ease with which a human reader can comprehend the purpose, control flow
In computer science, control flow (or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an ''imper ...
, and operation of source code. It affects the aspects of quality above, including portability, usability and most importantly maintainability.
Readability is important because programmers spend the majority of their time reading, trying to understand, reusing and modifying existing source code, rather than writing new source code. Unreadable code often leads to bugs, inefficiencies, and duplicated code. A study found that a few simple readability transformations made code shorter and drastically reduced the time to understand it.
Following a consistent programming style
Programming style, also known as code style, is a set of rules or guidelines used when writing the source code for a computer program. It is often claimed that following a particular programming style will help programmers read and understand sour ...
often helps readability. However, readability is more than just programming style. Many factors, having little or nothing to do with the ability of the computer to efficiently compile and execute the code, contribute to readability. Some of these factors include:
*Different indent style
In computer programming, an indentation style is a convention governing the indentation of blocks of code to convey program structure. This article largely addresses the free-form languages, such as C and its descendants, but can be (and often ...
s (whitespace)
* Comments
*Decomposition
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
*Naming conventions
A naming convention is a convention (generally agreed scheme) for naming things. Conventions differ in their intents, which may include to:
* Allow useful information to be deduced from the names based on regularities. For instance, in Manhatta ...
for objects (such as variables, classes, functions, procedures, etc.)
The presentation
A presentation conveys information from a speaker to an audience. Presentations are typically demonstrations, introduction, lecture, or speech meant to inform, persuade, inspire, motivate, build goodwill, or present a new idea/product. Presenta ...
aspects of this (such as indents, line breaks, color highlighting, and so on) are often handled by the source code editor
A source-code editor is a text editor program designed specifically for editing source code of computer programs. It may be a standalone application or it may be built into an integrated development environment (IDE) or web browser. Source-code ed ...
, but the content aspects reflect the programmer's talent and skills.
Various visual programming language
In computing, a visual programming language (visual programming system, VPL, or, VPS) is any programming language that lets users create programs by manipulating program elements ''graphically'' rather than by specifying them ''textually''. A VP ...
s have also been developed with the intent to resolve readability concerns by adopting non-traditional approaches to code structure and display. Integrated development environment
An integrated development environment (IDE) is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of at least a source code editor, build automation tools a ...
s (IDEs) aim to integrate all such help. Techniques like Code refactoring
In computer programming and software design, code refactoring is the process of restructuring existing computer code—changing the '' factoring''—without changing its external behavior. Refactoring is intended to improve the design, structur ...
can enhance readability.
Algorithmic complexity
The academic field and the engineering practice of computer programming are both largely concerned with discovering and implementing the most efficient algorithms for a given class of problems. For this purpose, algorithms are classified into ''orders'' using so-called Big O notation
Big ''O'' notation is a mathematical notation that describes the limiting behavior of a function when the argument tends towards a particular value or infinity. Big O is a member of a family of notations invented by Paul Bachmann, Edmund Lan ...
, which expresses resource use, such as execution time or memory consumption, in terms of the size of an input. Expert programmers are familiar with a variety of well-established algorithms and their respective complexities and use this knowledge to choose algorithms that are best suited to the circumstances.
Methodologies
The first step in most formal software development processes is requirements analysis
In systems engineering and software engineering, requirements analysis focuses on the tasks that determine the needs or conditions to meet the new or altered product or project, taking account of the possibly conflicting requirements of the ...
, followed by testing to determine value modeling, implementation, and failure elimination (debugging). There exist a lot of different approaches for each of those tasks. One approach popular for requirements analysis is Use Case
In software and systems engineering, the phrase use case is a polyseme with two senses:
# A usage scenario for a piece of software; often used in the plural to suggest situations where a piece of software may be useful.
# A potential scenario ...
analysis. Many programmers use forms of Agile software development
In software development, agile (sometimes written Agile) practices include requirements discovery and solutions improvement through the collaborative effort of self-organizing and cross-functional teams with their customer(s)/ end user(s), ad ...
where the various stages of formal software development are more integrated together into short cycles that take a few weeks rather than years. There are many approaches to the Software development process.
Popular modeling techniques include Object-Oriented Analysis and Design (OOAD
Object-oriented analysis and design (OOAD) is a technical approach for analyzing and designing an application, system, or business by applying object-oriented programming, as well as using visual modeling throughout the software development proces ...
) and Model-Driven Architecture (MDA
MDA, mda, or ''variation'', may refer to:
Places
* Moldova, a country in Europe with the ISO 3166-1 country code MDA Politics
* Meghalaya Democratic Alliance (2018), ruling coalition government in the Indian State of Meghalaya led by National Pe ...
). The Unified Modeling Language (UML
The Unified Modeling Language (UML) is a general-purpose, developmental modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system.
The creation of UML was originally m ...
) is a notation used for both the OOAD and MDA.
A similar technique used for database design is Entity-Relationship Modeling ( ER Modeling).
Implementation techniques include imperative languages (object-oriented
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...
or procedural), functional languages
In computer science, functional programming is a programming paradigm where programs are constructed by applying and composing functions. It is a declarative programming paradigm in which function definitions are trees of expressions that m ...
, and logic languages.
Measuring language usage
It is very difficult to determine what are the most popular modern programming languages. Methods of measuring programming language popularity include: counting the number of job advertisements that mention the language, the number of books sold and courses teaching the language (this overestimates the importance of newer languages), and estimates of the number of existing lines of code written in the language (this underestimates the number of users of business languages such as COBOL).
Some languages are very popular for particular kinds of applications, while some languages are regularly used to write many different kinds of applications. For example, COBOL
COBOL (; an acronym for "common business-oriented language") is a compiled English-like computer programming language designed for business use. It is an imperative, procedural and, since 2002, object-oriented language. COBOL is primarily us ...
is still strong in corporate data centers often on large mainframe computer
A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...
s, Fortran in engineering applications, scripting language
A scripting language or script language is a programming language that is used to manipulate, customize, and automate the facilities of an existing system. Scripting languages are usually interpreted at runtime rather than compiled.
A scripting ...
s in Web
Web most often refers to:
* Spider web, a silken structure created by the animal
* World Wide Web or the Web, an Internet-based hypertext system
Web, WEB, or the Web may also refer to:
Computing
* WEB, a literate programming system created by ...
development, and C in embedded software
Embedded software is computer software, written to control machines or devices that are not typically thought of as computers, commonly known as embedded systems. It is typically specialized for the particular hardware that it runs on and has time ...
. Many applications use a mix of several languages in their construction and use. New languages are generally designed around the syntax of a prior language with new functionality added, (for example C++
C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
adds object-orientation to C, and Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
adds memory management and bytecode
Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (norma ...
to C++, but as a result, loses efficiency and the ability for low-level manipulation).
Debugging
Debugging is a very important task in the software development process since having defects in a program can have significant consequences for its users. Some languages are more prone to some kinds of faults because their specification does not require compilers to perform as much checking as other languages. Use of a static code analysis
In computer science, static program analysis (or static analysis) is the analysis of computer programs performed without executing them, in contrast with dynamic program analysis, which is performed on programs during their execution.
The term i ...
tool can help detect some possible problems. Normally the first step in debugging is to attempt to reproduce the problem. This can be a non-trivial task, for example as with parallel processes or some unusual software bugs. Also, specific user environment and usage history can make it difficult to reproduce the problem.
After the bug is reproduced, the input of the program may need to be simplified to make it easier to debug. For example, when a bug in a compiler can make it crash when parsing
Parsing, syntax analysis, or syntactic analysis is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar. The term ''parsing'' comes from Lati ...
some large source file, a simplification of the test case that results in only few lines from the original source file can be sufficient to reproduce the same crash. Trial-and-error/divide-and-conquer is needed: the programmer will try to remove some parts of the original test case and check if the problem still exists. When debugging the problem in a GUI, the programmer can try to skip some user interaction from the original problem description and check if remaining actions are sufficient for bugs to appear. Scripting and breakpoint
In software development, a breakpoint is an intentional stopping or pausing place in a program, put in place for debugging purposes. It is also sometimes simply referred to as a pause.
More generally, a breakpoint is a means of acquiring knowle ...
ing is also part of this process.
Debugging is often done with IDEs. Standalone debuggers like GDB
The GNU Debugger (GDB) is a Software portability, portable debugger that runs on many Unix-like systems and works for many programming languages, including Ada (programming language), Ada, C (programming language), C, C++, Objective-C, Free Pasc ...
are also used, and these often provide less of a visual environment, usually using a command line
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
. Some text editors such as Emacs
Emacs , originally named EMACS (an acronym for "Editor MACroS"), is a family of text editors that are characterized by their extensibility. The manual for the most widely used variant, GNU Emacs, describes it as "the extensible, customizable, s ...
allow GDB to be invoked through them, to provide a visual environment.
Programming languages
Different programming languages support different styles of programming (called ''programming paradigm
Programming paradigms are a way to classify programming languages based on their features. Languages can be classified into multiple paradigms.
Some paradigms are concerned mainly with implications for the execution model of the language, suc ...
s''). The choice of language used is subject to many considerations, such as company policy, suitability to task, availability of third-party packages, or individual preference. Ideally, the programming language best suited for the task at hand will be selected. Trade-offs from this ideal involve finding enough programmers who know the language to build a team, the availability of compilers for that language, and the efficiency with which programs written in a given language execute. Languages form an approximate spectrum from "low-level" to "high-level"; "low-level" languages are typically more machine-oriented and faster to execute, whereas "high-level" languages are more abstract and easier to use but execute less quickly. It is usually easier to code in "high-level" languages than in "low-level" ones.
Programming languages are essential for software development. They are the building blocks for all software, from the simplest applications to the most sophisticated ones.
Allen Downey
Allen Benjamin Downey (born May 11, 1967) is an American computer scientist who is currently working as a Staff Scientist at DrivenData. He was a former Professor of Computer Science at the Franklin W. Olin College of Engineering.
Biography
D ...
, in his book ''How To Think Like A Computer Scientist'', writes:
:The details look different in different languages, but a few basic instructions appear in just about every language:
:*Input: Gather data from the keyboard, a file, or some other device.
:*Output: Display data on the screen or send data to a file or other device.
:*Arithmetic: Perform basic arithmetical operations like addition and multiplication.
:*Conditional Execution: Check for certain conditions and execute the appropriate sequence of statements.
:*Repetition: Perform some action repeatedly, usually with some variation.
Many computer languages provide a mechanism to call functions provided by shared libraries
In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subr ...
. Provided the functions in a library follow the appropriate run-time conventions (e.g., method of passing arguments
An argument is a statement or group of statements called premises intended to determine the degree of truth or acceptability of another statement called conclusion. Arguments can be studied from three main perspectives: the logical, the dialectic ...
), then these functions may be written in any other language.
Programmers
Computer programmers are those who write computer software. Their jobs usually involve:
*Prototyping
*Coding
*Debugging
*Documentation
Documentation is any communicable material that is used to describe, explain or instruct regarding some attributes of an object, system or procedure, such as its parts, assembly, installation, maintenance and use. As a form of knowledge manageme ...
*Integration
Integration may refer to:
Biology
*Multisensory integration
*Path integration
* Pre-integration complex, viral genetic material used to insert a viral genome into a host genome
*DNA integration, by means of site-specific recombinase technology, ...
*Maintenance
Maintenance may refer to:
Biological science
* Maintenance of an organism
* Maintenance respiration
Non-technical maintenance
* Alimony, also called ''maintenance'' in British English
* Champerty and maintenance, two related legal doctrine ...
*Requirements analysis
*Software architecture
Software architecture is the fundamental structure of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations.
...
*Software testing
*Specification
A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard.
There are different types of technical or engineering specificati ...
Although programming has been presented in the media as a somewhat mathematical subject, some research shows that good programmers have strong skills in natural human languages, and that learning to code is similar to learning a foreign language
A foreign language is a language that is not an official language of, nor typically spoken in, a given country, and that native speakers from that country must usually acquire through conscious learning - be this through language lessons at schoo ...
.
See also
* ACCU
*Association for Computing Machinery
The Association for Computing Machinery (ACM) is a US-based international learned society for computing. It was founded in 1947 and is the world's largest scientific and educational computing society. The ACM is a non-profit professional member ...
*Computer network
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
ing
*Hello world program
''Hello'' is a salutation or greeting in the English language. It is first attested in writing from 1826. Early uses
''Hello'', with that spelling, was used in publications in the U.S. as early as the 18 October 1826 edition of the ''Norwich C ...
*Institution of Analysts and Programmers
The Institution of Analysts and Programmers is a professional body that represents those working in Systems Analysis, Design, Programming and implementation of computer systems both in the United Kingdom and internationally. Established in 1972 ...
*National Coding Week Natinalniger Coding Week was founded by former headteacher Richard Rolfe and tech entrepreneur Jordan Love, who was appointed EU Code Week Ambassador for the UK. It took place during the week commencing September 21, 2014 with the aim of helping adu ...
*Object hierarchy
An object hierarchy is a concept from computer programming. It references descendants of objects acting as properties of an object. An example of this would be the object controlling a window
A window is an opening in a wall, door, roof, o ...
*Programming best practices
Coding best practices or programming best practices are a set of informal rules (''best practices'') that many software developers in computer programming follow to improve software quality.
Many computer programs remain in use for long periods of ...
*System programming Systems programming, or system programming, is the activity of programming computer system software. The primary distinguishing characteristic of systems programming when compared to application programming is that application programming aims to pr ...
*Computer programming in the punched card era
From the invention of computer programming languages up to the mid-1970s, most computer programmers created, edited and stored their programs line by line on punch cards.
Punched cards
A punched card is a flexible write-once medium that encod ...
*''The Art of Computer Programming
''The Art of Computer Programming'' (''TAOCP'') is a comprehensive monograph written by the computer scientist Donald Knuth presenting programming algorithms and their analysis. Volumes 1–5 are intended to represent the central core of compu ...
''
*Women in computing
Women in computing were among the first programmers in the early 20th century, and contributed substantially to the industry. As technology and practices altered, the role of women as programmers has changed, and the recorded history of the fiel ...
*Timeline of women in computing
This is a timeline of women in computing. It covers the time when women worked as "human computers" and then as programmers of physical computers. Eventually, women programmers went on to write software, develop Internet technologies and other ...
References
Sources
*
*
*
*
Further reading
* A.K. Hartmann,
Practical Guide to Computer Simulations
', Singapore: World Scientific
World Scientific Publishing is an academic publisher of scientific, technical, and medical books and journals headquartered in Singapore. The company was founded in 1981. It publishes about 600 books annually, along with 135 journals in various f ...
(2009)
* A. Hunt, D. Thomas, and W. Cunningham, ''The Pragmatic Programmer. From Journeyman to Master'', Amsterdam: Addison-Wesley Longman (1999)
* Brian W. Kernighan, ''The Practice of Programming'', Pearson (1999)
* Weinberg, Gerald M., ''The Psychology of Computer Programming'', New York: Van Nostrand Reinhold (1971)
* Edsger W. Dijkstra
Edsger Wybe Dijkstra ( ; ; 11 May 1930 – 6 August 2002) was a Dutch computer scientist, programmer, software engineer, systems scientist, and science essayist. He received the 1972 Turing Award for fundamental contributions to developing progra ...
, ''A Discipline of Programming'', Prentice-Hall (1976)
* O.-J. Dahl, E.W.Dijkstra, C.A.R. Hoare, ''Structured Programming'', Academic Press (1972)
* David Gries
David Gries (born April 26, 1939 in Flushing, Queens, New York) is an American computer scientist at Cornell University, United States mainly known for his books ''The Science of Programming'' (1981) and ''A Logical Approach to Discrete Math'' ( ...
, ''The Science of Programming'', Springer-Verlag (1981)
External links
*
*
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Programming