"Hello, World!" program#C++

{{Short description|Traditional first example of a computer programming language}}

{{Redirect-multi|2|Hello, World|Helloworld|other uses|Hello World (disambiguation)}}

A "Hello, World!" program is usually a simple computer program that emits (or displays) to the screen (often the console) a message similar to "Hello, World!". A small piece of code in most general-purpose programming languages, this program is used to illustrate a language's basic syntax. Such a program is often the first written by a student of a new programming language,{{cite book |last1=Langbridge |first1=James A. |url=https://books.google.com/books?id=y51NAgAAQBAJ&pg=PA74 |title=Professional Embedded ARM Development |date=3 December 2013 |publisher=John Wiley & Sons |isbn=9781118887820}} but it can also be used as a sanity check to ensure that the computer software intended to compile or run source code is correctly installed, and that its operator understands how to use it.

History

File:Hello World Brian Kernighan 1974.jpg and signed by Brian Kernighan (1978)]]

While several small test programs have existed since the development of programmable computers, the tradition of using the phrase "Hello, World!" as a test message was influenced by an example program in the 1978 book The C Programming Language,{{cite book |last1=Kernighan |first1=Brian W. |author1-link=Brian Kernighan |last2=Ritchie |first2=Dennis M. |author2-link=Dennis Ritchie |date=1978 |title=The C Programming Language |edition=1st |publisher=Prentice Hall |location=Englewood Cliffs, New Jersey |isbn=0-13-110163-3 |url-access=registration |url=https://archive.org/details/cprogramminglang00kern}} with likely earlier use in BCPL. The example program from the book prints {{samp|"hello, world"}}, and was inherited from a 1974 Bell Laboratories internal memorandum by Brian Kernighan, Programming in C: A Tutorial:{{cite web |url=https://www.bell-labs.com/usr/dmr/www/ctut.pdf |title=Programming in C: A Tutorial |last1=Kernighan |first1=Brian |author1-link=Brian Kernighan |year=1974 |publisher=Bell Labs |url-status=live |archive-url=https://web.archive.org/web/20220322215231/https://www.bell-labs.com/usr/dmr/www/ctut.pdf |archive-date=22 March 2022 |access-date=9 January 2019}}

main( ) {

printf("hello, world");

}

In the above example, the {{samp|main( )}} function defines where the program should start executing. The function body consists of a single statement, a call to the {{samp|printf()}} function, which stands for "print formatted"; it outputs to the console whatever is passed to it as the parameter, in this case the string {{samp|"hello, world"}}.

The C-language version was preceded by Kernighan's own 1972 A Tutorial Introduction to the Language B,{{cite book |last1=Johnson |first1=S. C. |last2=Kernighan |first2=B. W. |author2-link=Brian Kernighan |url=https://www.bell-labs.com/usr/dmr/www/bintro.html |title=The Programming Language B |publisher=Bell Labs |url-status=live |archive-url=https://web.archive.org/web/20150611114355/https://www.bell-labs.com/usr/dmr/www/bintro.html |archive-date=11 June 2015 |access-date=8 August 2024}} 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 prints {{samp|hello, world!}} on the terminal, including a newline character. The phrase is divided into multiple variables because in B a character constant is limited to four ASCII characters. The previous example in the tutorial printed {{samp|hi!}} on the terminal, and the phrase {{samp|hello, world!}} was introduced as a slightly longer greeting that required several character constants for its expression.

The Jargon File reports that "hello, world" instead originated in 1967 with the language BCPL.{{cite web |url=http://www.catb.org/jargon/html/B/BCPL.html |title=BCPL |work=Jargon File |access-date=21 April 2013 |archive-date=3 April 2018 |archive-url=https://web.archive.org/web/20180403000549/http://www.catb.org/jargon/html/B/BCPL.html |url-status=live}} Outside computing, use of the exact phrase began over a decade prior; it was the catchphrase of New York radio disc jockey William B. Williams beginning in the 1950s.{{cite web |url=https://select.nytimes.com/search/restricted/article?res=F50714FF3E5B0C778CDDA10894DE484D81| title=William B. Williams, Radio Personality, Dies |work=The New York Times |date=4 August 1986}}

Variations

Image:PSP-Homebrew.jpeg as a proof of concept]]

"Hello, World!" programs vary in complexity between different languages. In some languages, particularly scripting languages, the "Hello, World!" program can be written as one statement, while in others (more so many low-level languages) many more statements can be required. For example, in Python, to print the string {{samp|Hello, World!}} followed by a newline, one only needs to write print("Hello, World!"). In contrast, the equivalent code in C++{{cite web |url=https://en.wikibooks.org/wiki/C%2B%2B_Programming/Examples/Hello_world |title=C++ Programming/Examples/Hello world |publisher=Wikibooks |access-date=16 March 2022 |archive-date=28 March 2022 |archive-url=https://web.archive.org/web/20220328130457/https://en.wikibooks.org/wiki/C%2B%2B_Programming/Examples/Hello_world |url-status=live}} requires the import of the input/output (I/O) software library, the manual declaration of an entry point, and the explicit instruction that the output string should be sent to the standard output stream.

File:CNC Hello World.jpg (CNC) machining test in poly(methyl methacrylate) (Perspex).]]

The phrase "Hello, World!" has seen various deviations in casing and punctuation, such as "hello world" which lacks the capitalization of the leading H and W, 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 some esoteric programming languages may have to print a slightly modified string. Other human languages have been used as the output; for example, a tutorial for the Go language emitted both English and Chinese or Japanese characters, demonstrating the language's built-in Unicode support.[http://golang.org/doc/go_tutorial.html#tmp_20 A Tutorial for the Go Programming Language.] {{webarchive |url=https://web.archive.org/web/20100726052120/http://golang.org/doc/go_tutorial.html#tmp_20 |date=26 July 2010}} The Go Programming Language. Retrieved 26 July 2011. Another notable example is the Rust language, whose management system automatically inserts a "Hello, World" program when creating new projects.

File:HelloWorld Maktivism ComputerProgramming LEDs.jpg with a moving strip of light-emitting diodes (LEDs)]]

Some languages change the function of the "Hello, World!" program while maintaining the spirit of demonstrating a simple example. Functional programming languages, such as Lisp, ML, and Haskell, tend to substitute a factorial program 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 producing side effects. Languages otherwise able to print "Hello, World!" (assembly language, C, VHDL) may also be used in embedded systems, where text output is either difficult (requiring added components or communication with another computer) or nonexistent. For devices such as microcontrollers, field-programmable gate arrays, and complex programmable logic devices (CPLDs), "Hello, World!" may thus be substituted with a blinking light-emitting diode (LED), which demonstrates timing and interaction between components.{{cite web|last1=Silva|first1=Mike|title=Introduction to Microcontrollers - Hello World|url=http://www.embeddedrelated.com/showarticle/460.php|website=EmbeddedRelated.com|access-date=19 May 2015|date=11 September 2013|archive-date=22 May 2015|archive-url=https://web.archive.org/web/20150522081938/http://www.embeddedrelated.com/showarticle/460.php|url-status=live}}{{cite web|last1=George|first1=Ligo|title=Blinking LED using Atmega32 Microcontroller and Atmel Studio|url=https://electrosome.com/blinking-led-atmega32-avr-microcontroller/|website=electroSome|date=8 May 2013|access-date=19 May 2015|archive-date=5 November 2014|archive-url=https://web.archive.org/web/20141105123532/http://electrosome.com/blinking-led-atmega32-avr-microcontroller|url-status=live}}{{cite web|last1=PT|first1=Ranjeeth|title=2. AVR Microcontrollers in Linux HOWTO|url=http://www.tldp.org/HOWTO/Avr-Microcontrollers-in-Linux-Howto/x207.html|website=The Linux Documentation Project|access-date=19 May 2015|archive-date=2 May 2015|archive-url=https://web.archive.org/web/20150502194301/http://www.tldp.org/HOWTO/Avr-Microcontrollers-in-Linux-Howto/x207.html|url-status=live}}{{cite web|last1=Andersson|first1=Sven-Åke|title=3.2 The first Altera FPGA design|url=http://www.rte.se/blog/blogg-modesty-corex/first-altera-fpga-design/3.2|publisher=Raidió Teilifís Éireann|access-date=19 May 2015|date=2 April 2012|archive-url=https://web.archive.org/web/20150521222132/http://www.rte.se/blog/blogg-modesty-corex/first-altera-fpga-design/3.2|archive-date=21 May 2015|url-status=dead}}{{cite web|last1=Fabio|first1=Adam|title=CPLD Tutorial: Learn programmable logic the easy way|url=http://hackaday.com/2014/04/06/cpld-tutorial-learn-programmable-logic-the-easy-way/|website=Hackaday|access-date=19 May 2015|date=6 April 2014|archive-date=20 May 2015|archive-url=https://web.archive.org/web/20150520063507/http://hackaday.com/2014/04/06/cpld-tutorial-learn-programmable-logic-the-easy-way/|url-status=live}}

The Debian and Ubuntu Linux distributions provide the "Hello, World!" program through their software package manager systems, which can be invoked with the command {{samp|hello}}. It serves as a sanity check and a simple example of installing a software package. For developers, it provides an example of creating a .deb package, either traditionally or using debhelper, and the version of {{samp|hello}} used, GNU Hello, serves as an example of writing a GNU program.{{cite web|title=Hello |url=https://www.gnu.org/software/hello/|website=GNU Project |publisher=Free Software Foundation |access-date=7 July 2017|archive-url=https://archive.today/20140529011826/http://www.gnu.org/software/hello/|archive-date=29 May 2014|url-status=dead}}

Variations of the "Hello, World!" program that produce a graphical output (as opposed to text output) have also been shown. Sun demonstrated a "Hello, World!" program in Java based on scalable vector graphics,{{cite news|last=Jolif|first=Christophe|title=Bringing SVG Power to Java Applications|newspaper=Sun Developer Network|date=January 2003}} and the XL programming language features a spinning Earth "Hello, World!" using 3D computer graphics.{{cite web|last=de Dinechin|first=Christophe|title=Hello world!|url=http://grenouillebouillie.wordpress.com/2010/07/24/hello-world/|publisher=Grenouille Bouillie|date=24 July 2010}} Mark Guzdial and Elliot Soloway have suggested that the "hello, world" test message may be outdated now that graphics and sound can be manipulated as easily as text.{{cite web|url=http://www.bfoit.org/itp/Soloway/CACM_Nintendo_Generation.pdf|title=Teaching the Nintendo Generation to Program|website=bfoit.org|access-date=27 December 2015|archive-url=https://web.archive.org/web/20160505190520/http://www.bfoit.org/itp/Soloway/CACM_Nintendo_Generation.pdf|archive-date=5 May 2016|url-status=dead}}

In computer graphics, rendering a triangle{{snd}}called "Hello Triangle"{{snd}}is sometimes used as an introductory example for graphics libraries.{{Cite book |last=Vries |first=Joey de |title=Learn OpenGL - Graphics Programming |date= |publisher=Kendall & Welling |year=2020 |isbn=978-90-90-33256-7 |pages=26}}{{cite magazine|magazine=The MagPi|issue=65|date=Jan 2018|title=Coding games on the Raspberry Pi in C/C++ Part 01|page=57|quote=next time we will expand our code to start working with graphics and the famous 'hello triangle' code that absolutely no one uses except game coders|first1=Brian|last1=Beuken}}

Time to Hello World

"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.{{cite book |last1=O'Dwyer |first1=Arthur |title=Mastering the C++17 STL: Make full use of the standard library components in C++17 |date=September 2017 |publisher=Packt Publishing Ltd |isbn=978-1-78728-823-2 |page=251 |url=https://books.google.com/books?id=zJlGDwAAQBAJ&q=%22TTHW%22&pg=PA251 |access-date=4 December 2019 |language=en}} For instance, the first publicly known "Hello, World!" program in Malbolge (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 in Common Lisp {{see above|{{slink||Variations}}, above}}.

The concept has been extended beyond programming languages to APIs, 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.{{cite web |last1=Wiegers |first1=Harold |title=The importance of "Time to First Hello, World!" an efficient API program |date=28 June 2018 |url=https://apifriends.com/api-management/api-program-time-first-hello-world/ |access-date=19 February 2020 |archive-date=19 February 2020 |archive-url=https://web.archive.org/web/20200219061813/https://apifriends.com/api-management/api-program-time-first-hello-world/ |url-status=live}}{{cite book |last1=Jin |first1=Brenda |last2=Sahni |first2=Saurabh |last3=Shevat |first3=Amir |title=Designing Web APIs: Building APIs That Developers Love |url=https://books.google.com/books?id=Dg1rDwAAQBAJ&q=%22time%20to%20hello%20world%22&pg=PT150 |date=29 August 2018 |publisher=O'Reilly Media |isbn=9781492026877 |access-date=19 February 2020}}

Wikipedia articles containing "Hello, World!" programs

{{flatlist|*ABAP

References

External links

[https://helloworldcollection.de The Hello World Collection]
{{cite web |title=Hello world/Text |url=https://rosettacode.org/wiki/Hello_world/Text |work=Rosetta Code |date=23 May 2024}}
{{cite web |title=GitHub – leachim6/hello-world: Hello world in every computer language. Thanks to everyone who contributes to this, make sure to see CONTRIBUTING.md for contribution instructions! |website=GitHub |date=30 October 2021|url=https://github.com/leachim6/hello-world}}
{{cite web |title=Unsung Heroes of IT: Part One: Brian Kernighan |url=http://theunsungheroesofit.com/helloworld/ |work=TheUnsungHeroesOfIT.com |access-date=23 August 2014 |archive-url=https://web.archive.org/web/20160326193543/http://theunsungheroesofit.com/helloworld/ |archive-date=26 March 2016 |url-status=dead}}

Category:Test items in computer languages

Category:Computer programming folklore

Category:Articles with example code

Category:Articles with quotation marks in the title