Hello, world!: Wikis


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A GUI "Hello World" program, written in Perl
Hackers can execute unsigned HelloWorld code on Sony's PlayStation Portable.
A light-programmable biofilm displaying the Hello World message
CNC machining test in Perspex

A "Hello World" program is a computer program which prints out "Hello, world!" on a display device. It is used in many introductory tutorials for teaching a programming language. Such a program is typically one of the simplest programs possible in most computer languages. It is often considered to be tradition among programmers for people attempting to learn a new programming language to write a "Hello World!" program as one of the first steps of learning that particular language. Some are surprisingly complex, especially in some graphical user interface (GUI) contexts, but most are very simple, especially those which rely heavily on a particular command line interpreter ("shell") to perform the actual output. In an embedded system, the text may be sent to a liquid crystal display (LCD), or the message may be substituted by some other appropriate signal, such as an LED being turned on.

Contents

Purpose

A "hello world" program has become the traditional first program that many people learn. In general, it is simple enough that people who have no previous experience with computer programming can easily understand it, especially with the guidance of a teacher or a written guide. Using this simple program as a basis, computer science principles or elements of a specific programming language can be explained to novice programmers. Experienced programmers learning new languages can also gain a lot of information about a given language's syntax and structure from a hello world program.

In addition, hello world can be a useful sanity test to make sure that a language's compiler, development environment, and run-time environment are correctly installed. Configuring a complete programming toolchain from scratch to the point where even trivial programs can be compiled and run can involve substantial amounts of work. For this reason, a simple program is used first when testing a new tool chain.

"Hello world" is also used by computer hackers as a proof of concept that arbitrary code can be executed through an exploit where code should not be allowed to be executed, for example, on Sony's Playstation Portable. This is the first step into making home-made content ("homebrew") usable on such a device.

History

While small test programs 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 seminal book The C Programming Language. The example program from that book prints "hello, world" (without capital letters or exclamation mark), and was inherited from a 1974 Bell Laboratories internal memorandum by Brian Kernighan, Programming in C: A Tutorial, which contains the first known version:

 int main() 
 {
        printf("hello, world");
        return 0;
 }

The first known instance of the usage of the words "hello" and "world" together in computer literature occurred earlier, in Kernighan's 1972 Tutorial Introduction to the Language B[1], with the following code:

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

Variations

There are many variations on the punctuation and casing of the phrase. Variations include the presence or absence of the comma and exclamation mark, and the capitalization of the 'H', both the 'H' and the 'W', or neither. Some languages are forced to implement different forms, such as "HELLO WORLD!", on systems that only support capital letters, while many "hello world" programs in esoteric languages print out a slightly modified string. For example, the first non-trivial Malbolge program printed "HEllO WORld", this having been determined to be good enough.

There are variations in spirit, as well. Functional programming languages, like Lisp, ML and Haskell, tend to substitute a factorial program for Hello World, as the former emphasizes recursive techniques, which are a big part of functional programming, while the latter emphasizes I/O, which violates the spirit of pure functional programming by producing side effects.

The Debian and Ubuntu Linux distributions provide the "hello world" program through the apt packaging system; this allows users to simply type "apt-get install hello" for the program to be installed, along with any software dependencies. While of itself useless, it serves as a sanity check and a simple example to newcomers of how to install a package. It is significantly more useful for developers, however, as it provides an example of how to create a .deb package, either traditionally or using debhelper, and the version of hello used, GNU hello, serves as an example of how to write a GNU program.[2]

See also

References

External links


Study guide

Up to date as of January 14, 2010

From Wikiversity

Hello, world! is a classic "first program" one creates when learning a new programming language. The objective of the application is the same: to print the text "Hello, world!" to the screen in some form, be it console output or a dialog.

In many cases, the statement required to do this is a single line.

It seems appropriate that our introduction to Computer Science occupied this title. As a student, the first choice to make is to decide what kind of knowledge you are looking for. Of course, this depends upon your needs. You might be:

  • A learned computer scientist or professional eager to contribute research and course material
  • Computer professional seeking an alternative to expensive commercial certification
  • Adult non-computer professional or entrepreneur who could benefit from academic/practical knowledge of computing
  • College-eligible (or not) student considering a degree
  • Casual user trying to to catch/spread the next virus
  • Hobbyist or computer gamer looking to get the most out of your computing experience
  • Complete newbie looking for a place to start

This is an exciting time for education, and for those of us wishing to collaborate and share knowledge, skills and experience. At present, we are only limited by the sky, and some very large hard drives in a server farm somewhere.

Contents

Examples of Hello, world!

Ada

 with Ada.Text_IO;
 
 procedure Hello is
 begin
    Ada.Text_IO.Put_Line ("Hello, world!");
 end Hello;

For an explanation see b:Ada Programming:Basic.

ASP

<%
    Response.Write "Hello, world!"
%>

or

<%="Hello, World!"%>

Assembly

x86 compatible

 title Hello World Program 
 dosseg 
 .model small 
 .stack 100h 
 .data 
 hello_message db 'Hello, world!',0dh,0ah,'$' 
 .code
  main  proc
     mov    ax,@data
     mov    ds,ax
     mov    ah,9
     mov    dx,offset hello_message
     int    21h
     mov    ax,4C00h
     int    21h
 main  endp
 end   main

BASH

#!/bin/bash
echo "Hello, world!"

BASIC

Applesoft BASIC

Used on Apple ][ machines (Apple ][+, ][e, //c, ][GS)

10 PRINT "HELLO, WORLD!"

-or-

10 ? "HELLO, WORLD!"

Bally/Astrocade Basic

As used on the Bally and Astrocade game systems ca. 1978

10 PRINT "HELLO, WORLD!"

Commodore BASIC

As used on a Commodore 64, ca. 1984

10 ? "Hello, world!"

Dark Basic

PRINT "Hello, world!"

FreeBASIC and QuickBASIC

PRINT "Hello, world!"
SLEEP

Intellivision Basic

As used on a Mattel Intellivision, ca. 1983

10 PRINT "HELLO, WORLD!"

Intellivision ECS Basic

As used in the Mattel Intellivision ECS

10 PRIN "HELLO, WORLD."

! not on ECS keyboard. Only 4 char. commands in ECS Basic

Liberty BASIC

PRINT "Hello, world!"

Batch

@ECHO OFF
echo Hello, World!

C

#include <stdio.h>
 
int main(void) 
{
  printf( "Hello, world!\n" );
  return 0;
}

C#

using System;
 
namespace HelloWorld
{
  class Program 
  {
    static void Main() 
    {
      Console.WriteLine("Hello, world!");
    }
  }
}

C++

#include <iostream>
using namespace std;
 
int main()
{
  cout << "Hello, world!\n";
  return 0;
}

COBOL

000100 IDENTIFICATION DIVISION. PROGRAM-ID.     HELLOWORLD. PROCEDURE DIVISION.     DISPLAY "Hello, 
world!"

Common Lisp

(print "Hello, world!")

Or:

(format t "Hello, world!~%")

Delphi

begin
  Writeln('Hello, world!');
end.

Eztrieve (IBM Mainframe programming language).

JOB NULL

DISPLAY "HELLO, WORLD"

STOP

Forth

: HELLO    ." Hello, world!"  ;
HELLO

Fortran

    PROGRAM HELLO
    PRINT *,'Hello, world'
    STOP
    END

Haskell

main :: IO ()
main = putStrLn "Hello, world!"

Html

<html>
<head>
<title>Hello, world!</title>
</head>
<body>
<p>
Hello, world!
</p>
</body>
</html>

JavaScript (aka JScript, ECMAScript, LiveScript)

document.println("Hello, world!");

or

alert("Hello, world!");

or

document.writeln("Hello, world!");

Luka

print "Hello, world"

or, with proper syntax

print( "Hello, world!" );

Oberon

MODULE Hello;

   IMPORT Out;

   PROCEDURE World*;
   BEGIN
      Out.Open;
      Out.String("Hello, world!"); Out.Ln;
   END World;

END Hello.

OCaml

print_endline "Hello, world!"

Pascal

program HelloWorld;
begin
  writeln( 'Hello, world!' );
end.

Perl

#!/usr/bin/perl
print "Hello, world!\n";

PHP

<?php
echo "Hello, world!";
?>

or (with short_tags enabled in php.ini)

<? echo "Hello, world!"; ?>

or (with asp_tags enabled in php.ini)

<% echo "Hello, world!"; %>

or

<?="Hello, world!"?>

Python

#!/usr/bin/env python
print 'Hello, world!'

The first line is used on Unix systems only, and is optional even there. The advantage is that it allows the file to be invoked directly (if chmod +x), without explicitly specifying the python interpreter.

Ruby

puts 'Hello, world!'

Another way to do it, albeit more obscure:

#!/usr/local/bin/ruby
puts 1767707668033969.to_s(36)

Tcl

#!/usr/bin/tclsh
puts "Hello, world!"

Trekkie

"Computer?"
*Bee bee boo
"Create program 'Hello, World! Picard-alpha-1'"
*Boo boo bee
"Parameters: Display the phrase 'Hello, world!' on the screen the program is executed from until the 
program is terminated."
*Bee bee
"Save program."
*Boo bee boo

Turing

put "Hello World!"

Visual Basic 6

Sub Main()
    MsgBox "VB6 este extraordinar !"
msgbox "Mi-a placut enorm Visual Basic !"
End Sub

Assignment

Create a Hello, world! program in a language not listed above, then edit this page and add it to the collection.

 Sub Main()
   Console.WriteLine("Hello, World")
 End Sub

Natural

WRITE 'Hello, world!'
END

Hello, world!

More about Computer Programming

See also








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