Wikipedia

"Hello, World!" program

"Hello, World" and "Helloworld" redirect here. For other uses, seeHello World (disambiguation).

A"Hello, World!" programis usually a simplecomputer programthat emits (or displays) to the screen (often theconsole) a message similar to "Hello, World!". A small piece of code in mostgeneral-purpose programming languages,this program is used to illustrate a language's basicsyntax.Such program is often the first written by a student of a new programming language,[1]but such a program can also be used as asanity checkto ensure that thecomputer softwareintended tocompileor runsource codeis correctly installed, and that its operator understands how to use it.

History

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"Hello, World!" program handwritten in theC languageand signed byBrian Kernighan(1978)

While several small test programs have existed since the development of programmablecomputers,the tradition of using the phrase "Hello, World!" as a test message was influenced by an example program in the 1978 bookThe C Programming Language,[2]with likely earlier use inBCPL.The example program from the book prints"hello, world",and was inherited from a 1974Bell Laboratoriesinternal memorandum byBrian Kernighan,Programming in C: A Tutorial:[3] 

main(){
printf("hello, world");
}

In the above example, themain( )functiondefines where the programshould start executing.The function body consists of a singlestatement,a call to theprintf()function, which stands for "print formatted "; it outputs to theconsolewhatever is passed to it as theparameter,in this case thestring"hello, world".

The C-language version was preceded by Kernighan's own 1972A Tutorial Introduction to the LanguageB,[4]where the first known version of the program is found in an example used to illustrate external variables: 

main( ) {
extrn a, b, c;
putchar(a); putchar(b); putchar(c); putchar('!*n');
}

a 'hell';
b 'o, w';
c 'orld';

The program above printshello, world!on the terminal, including anewlinecharacter. The phrase is divided into multiple variables because in B a character constant is limited to fourASCIIcharacters. The previous example in the tutorial printedhi!on the terminal, and the phrasehello, world!was introduced as a slightly longer greeting that required several character constants for its expression.

TheJargon Filereports that "hello, world" instead originated in 1967 with the languageBCPL.[5]Outside computing, use of the exact phrase began over a decade prior; it was thecatchphraseof New York radio disc jockeyWilliam B. Williamsbeginning in the 1950s.[6]

Variations

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A "Hello, World!" program running on Sony'sPlayStation Portableas aproof of concept

"Hello, World!" programs vary in complexity between different languages. In some languages, particularlyscripting languages,the "Hello, World!" program can be written as one statement, while in others (more so manylow-level languages) many more statements can be required. For example, inPython,to print the stringHello, World!followed by a newline, one only needs to writeprint("Hello, World!").In contrast, the equivalent code inC++[7]requires the import of theinput/output(I/O)software library,the manual declaration of anentry point,and the explicit instruction that the output string should be sent to thestandard outputstream.

Computernumerical control(CNC) machining test inpoly(methyl methacrylate)(Perspex).

The phrase "Hello, World!" has seen various deviations in casing and punctuation, such as the capitalization of the leadingHandW,and the presence of the comma or exclamation mark. Some devices limit the format to specific variations, such as all-capitalized versions on systems that support only capital letters, while someesoteric programming languagesmay have to print a slightly modified string. For example, the first non-trivialMalbolgeprogram printed "HEllO WORld", this having been determined to begood enough.[8][unreliable source?]Other human languages have been used as the output; for example, a tutorial for theGo languageemitted both English and Chinese or Japanese characters, demonstrating the language's built-inUnicodesupport.[9]Another notable example is theRust language,whose management system automatically inserts a "Hello, World" program when creating new projects.

A "Hello, World!" message being displayed through long-exposurelight paintingwith a moving strip oflight-emitting diodes(LEDs)

Some languages change the function of the "Hello, World!" program while maintaining the spirit of demonstrating a simple example.Functional programminglanguages, such asLisp,ML,andHaskell,tend to substitute afactorialprogram for "Hello, World!", as functional programming emphasizes recursive techniques, whereas the original examples emphasize I/O, which violates the spirit of pure functional programming by producingside effects.Languages otherwise able to print "Hello, World!" (assembly language,C,VHDL) may also be used inembedded systems,where text output is either difficult (requiring added components or communication with another computer) or nonexistent. For devices such asmicrocontrollers,field-programmable gate arrays,andcomplex programmable logic devices(CPLDs), "Hello, World!" may thus be substituted with a blinkinglight-emitting diode(LED), which demonstrates timing and interaction between components.[10][11][12][13][14]

TheDebianandUbuntuLinux distributionsprovide the "Hello, World!" program through theirsoftware package managersystems, which can be invoked with the commandhello.It serves as asanity checkand a simple example of installing a software package. For developers, it provides an example of creating a.debpackage, either traditionally or usingdebhelper,and the version ofhelloused,GNU Hello,serves as an example of writing aGNUprogram.[15]

Variations of the "Hello, World!" program that produce agraphical output(as opposed to text output) have also been shown.Sundemonstrated a "Hello, World!" program inJavabased onscalable vector graphics,[16]and theXLprogramming language features a spinning Earth "Hello, World!" using3D computer graphics.[17]Mark Guzdial andElliot Solowayhave suggested that the "hello, world" test message may be outdated now that graphics and sound can be manipulated as easily as text.[18]

Time to Hello World

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"Time to hello world" (TTHW) is the time it takes to author a "Hello, World!" program in a given programming language. This is one measure of a programming language's ease of use. Since the program is meant as an introduction for people unfamiliar with the language, a more complex "Hello, World!" program may indicate that the programming language is less approachable.[19]For instance, the first publicly known "Hello, World!" program inMalbolge(which actually output "HEllO WORld" ) took two years to be announced, and it was produced not by a human but by a code generator written inCommon Lisp(see§ Variations,above).

The concept has been extended beyond programming languages toAPIs,as a measure of how simple it is for a new developer to get a basic example working; a shorter time indicates an easier API for developers to adopt.[20][21]

Wikipedia articles containing "Hello, World!" programs

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See also

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References

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  1. ^Langbridge, James A. (3 December 2013).Professional Embedded ARM Development.John Wiley & Sons.ISBN9781118887820.
  2. ^Kernighan, Brian W.;Ritchie, Dennis M.(1978).The C Programming Language(1st ed.).Englewood Cliffs, New Jersey:Prentice Hall.ISBN0-13-110163-3.
  3. ^Kernighan, Brian(1974)."Programming in C: A Tutorial"(PDF).Bell Labs.Archived(PDF)from the original on 22 March 2022.Retrieved9 January2019.
  4. ^Johnson, S. C.;Kernighan, B. W.The Programming Language B.Bell Labs.Archivedfrom the original on 11 June 2015.Retrieved8 August2024.
  5. ^"BCPL".Jargon File.Archivedfrom the original on 3 April 2018.Retrieved21 April2013.
  6. ^"William B. Williams, Radio Personality, Dies".The New York Times.4 August 1986.
  7. ^"C++ Programming/Examples/Hello world".Wikibooks.Archivedfrom the original on 28 March 2022.Retrieved16 March2022.
  8. ^"Malbolge".Esolang.esolangs-wiki.Archivedfrom the original on 27 August 2022.Retrieved28 October2016.
  9. ^A Tutorial for the Go Programming Language.Archived26 July 2010 at theWayback MachineThe Go Programming Language. Retrieved 26 July 2011.
  10. ^Silva, Mike (11 September 2013)."Introduction to Microcontrollers - Hello World".EmbeddedRelated.com.Archivedfrom the original on 22 May 2015.Retrieved19 May2015.
  11. ^George, Ligo (8 May 2013)."Blinking LED using Atmega32 Microcontroller and Atmel Studio".electroSome.Archivedfrom the original on 5 November 2014.Retrieved19 May2015.
  12. ^PT, Ranjeeth."2. AVR Microcontrollers in Linux HOWTO".The Linux Documentation Project.Archivedfrom the original on 2 May 2015.Retrieved19 May2015.
  13. ^Andersson, Sven-Åke (2 April 2012)."3.2 The first Altera FPGA design".Raidió Teilifís Éireann. Archived fromthe originalon 21 May 2015.Retrieved19 May2015.
  14. ^Fabio, Adam (6 April 2014)."CPLD Tutorial: Learn programmable logic the easy way".Hackaday.Archivedfrom the original on 20 May 2015.Retrieved19 May2015.
  15. ^"Hello".GNU Project.Free Software Foundation. Archived fromthe originalon 29 May 2014.Retrieved7 July2017.
  16. ^Jolif, Christophe (January 2003). "Bringing SVG Power to Java Applications".Sun Developer Network.
  17. ^de Dinechin, Christophe (24 July 2010)."Hello world!".Grenouille Bouillie.
  18. ^"Teaching the Nintendo Generation to Program"(PDF).bfoit.org.Archived fromthe original(PDF)on 5 May 2016.Retrieved27 December2015.
  19. ^O'Dwyer, Arthur (September 2017).Mastering the C++17 STL: Make full use of the standard library components in C++17.Packt Publishing Ltd.p. 251.ISBN978-1-78728-823-2.Retrieved4 December2019.
  20. ^Wiegers, Harold (28 June 2018)."The importance of" Time to First Hello, World! "an efficient API program".Archivedfrom the original on 19 February 2020.Retrieved19 February2020.
  21. ^Jin, Brenda; Sahni, Saurabh; Shevat, Amir (29 August 2018).Designing Web APIs: Building APIs That Developers Love.O'Reilly Media.ISBN9781492026877.Retrieved19 February2020.
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