Computer programming often shortened to programming is a process that leads from an original formulation of a computing problem to executable computer programs Programming involves activities such as analysis developing understanding generating algorithms verification of requirements of algorithms including their correctness and resources consumption and implementation commonly referred to as coding of algorithms in a target programming language Source code is written in one or more programming languages The purpose of programming is to find a sequence of instructions that will automate performing a specific task or solving a given problem The process of programming thus often requires expertise in many different subjects including knowledge of the application domain specialized algorithms and formal logic
Related tasks include testing debugging and maintaining the source code implementation of the build system and management of derived artifacts such as machine code of computer programs These might be considered part of the programming process but often the term software development is used for this larger process with the term programming implementation or coding reserved for the actual writing of source code Software engineering combines engineering techniques with software development practices
Within software engineering programming the implementation is regarded as one phase in a software development process
There is an ongoing debate on the extent to which the writing of programs is an art form a craft or an engineering discipline In general good programming is considered to be the measured application of all three with the goal of producing an efficient and evolvable software solution the criteria for efficient and evolvable vary considerably The discipline differs from many other technical professions in that programmers in general do not need to be licensed or pass any standardized or governmentally regulated certification tests in order to call themselves programmers or even software engineers Because the discipline covers many areas which may or may not include critical applications it is debatable whether licensing is required for the profession as a whole In most cases the discipline is self-governed by the entities which require the programming and sometimes very strict environments are defined eg United States Air Force use of AdaCore and security clearance However representing oneself as a professional software engineer without a license from an accredited institution is illegal in many parts of the world
Another ongoing debate is the extent to which the programming language used in writing computer programs affects the form that the final program takes This debate is analogous to that surrounding the SapirWhorf hypothesis in linguistics and cognitive science which postulates that a particular spoken languages nature influences the habitual thought of its speakers Different language patterns yield different patterns of thought This idea challenges the possibility of representing the world perfectly with language because it acknowledges that the mechanisms of any language condition the thoughts of its speaker community
Ancient cultures seemed to have no conception of computing beyond arithmetic algebra and geometry occasionally devising computational systems with elements of calculus eg the method of exhaustion The only mechanical device that existed for numerical computation at the beginning of human history was the abacus invented in Sumeria circa  BC Later the Antikythera mechanism invented some time around  BC in ancient Greece is the first known mechanical calculator utilizing gears of various sizes and configuration to perform calculations which tracked the metonic cycle still used in lunar-to-solar calendars and which is consistent for calculating the dates of the Olympiads
The Kurdish medieval scientist Al-Jazari built programmable automata in  AD One system employed in these devices was the use of pegs and cams placed into a wooden drum at specific locations which would sequentially trigger levers that in turn operated percussion instruments The output of this device was a small drummer playing various rhythms and drum patterns The Jacquard loom which Joseph Marie Jacquard developed in  uses a series of pasteboard cards with holes punched in them The hole pattern represented the pattern that the loom had to follow in weaving cloth The loom could produce entirely different weaves using different sets of cards
Charles Babbage adopted the use of punched cards around  to control his Analytical Engine Mathematician Ada Lovelace theorized beyond the original intent of the Analytical Engine and how it could compute symbols as well as numbers building the foundation of modern programming That the engine might act upon other things besides number were objects found whose mutual fundamental relations could be expressed by those of the abstract science of operations and which should be also susceptible of adaptations to the action of the operating notation and mechanism of the engine She wrote a program for the engine to calculate a sequence of Bernoulli numbers becoming the worlds first programmer
In the s Herman Hollerith invented the recording of data on a medium that could then be read by a machine Prior uses of machine readable media above had been for lists of instructions not data to drive programmed machines such as Jacquard looms and mechanized musical instruments After some initial trials with paper tape he settled on punched cards To process these punched cards first known as Hollerith cards he invented the keypunch sorter and tabulator unit record machines These inventions were the foundation of the data processing industry In  he founded the Tabulating Machine Company which later became the core of IBM The addition of a control panel plugboard to his  Type I Tabulator allowed it to do different jobs without having to be physically rebuilt By the late s there were several unit record calculators such as the IBM  and IBM  whose control panels specified a sequence list of operations and thus were programmable machines
The invention of the von Neumann architecture allowed computer programs to be stored in computer memory Early programs had to be painstakingly crafted using the instructions elementary operations of the particular machine often in binary notation Every model of computer would likely use different instructions machine language to do the same task Later assembly languages were developed that let the programmer specify each instruction in a text format entering abbreviations for each operation code instead of a number and specifying addresses in symbolic form eg ADD X TOTAL Entering a program in assembly language is usually more convenient faster and less prone to human error than using machine language but because an assembly language is little more than a different notation for a machine language any two machines with different instruction sets also have different assembly languages
The synthesis of numerical calculation predetermined operation and output along with a way to organize and input instructions in a manner relatively easy for humans to conceive and produce led to the modern development of computer programming In  FORTRAN was invented it was the first widely-used high level programming language to have a functional implementation as opposed to just a design on paper A high-level language is in very general terms any programming language that allows the programmer to write programs in terms that are more abstract than assembly language instructions ie at a level of abstraction higher than that of an assembly language It allowed programmers to specify calculations by entering a formula directly eg Y  X  X   The program text or source is converted into machine instructions using a special program called a compiler which translates the FORTRAN program into machine language In fact the name FORTRAN stands for Formula Translation Many other languages were developed including some for commercial programming such as COBOL Programs were mostly still entered using punched cards or paper tape See computer programming in the punch card era By the late s data storage devices and computer terminals became inexpensive enough that programs could be created by typing directly into the computers Text editors were developed that allowed changes and corrections to be made much more easily than with punched cards Usually an error in punching a card meant that the card had to be discarded and a new one punched to replace it
As time has progressed computers have made giant leaps in processing power which have allowed the development of programming languages that are more abstracted from the underlying hardware Popular programming languages of the modern era include ActionScript C C C Haskell Java JavaScript Objective-C Perl PHP Python Ruby Smalltalk SQL Visual Basic and dozens more Although these high-level languages usually incur greater overhead the increase in speed of modern computers has made the use of these languages much more practical than in the past These increasingly abstracted languages are typically easier to learn and allow the programmer to develop applications much more efficiently and with less source code However high-level languages are still impractical for a few programs such as those where low-level hardware control is necessary or where maximum processing speed is vital Computer programming has become a popular career in the developed world particularly in the United States Europe and Japan Due to the high labor cost of programmers in these countries some forms of programming have been increasingly subject to outsourcing importing software and services from other countries usually at a lower wage making programming career decisions in developed countries more complicated while increasing economic opportunities for programmers in less developed areas particularly China and India