In a language of your choice, write a program that exactly outputs the characters Hello world! followed by a newline. The code:

  • should not use any character more than twice (alphanumeric, symbol, whitespace...anything)
  • should not use any external resources
  • should not use any user input
  • should not output anything else

An example of a valid python program:

print("He%so world!"%(2*'l'))

An example of an invalid python program (the character 'r' is used three times):

print("Hel"+chr(108)+'o world!')

Winner is whoever has the most votes after 14 days.

EDIT: A winner has been chosen! Thanks all for your work on this question!

  • 25
    \$\begingroup\$ What about the repeated letter o in the "valid" python example. There also these:- " ' ( ) \$\endgroup\$ Jan 17, 2014 at 16:35
  • 15
    \$\begingroup\$ @AdamSpeight what do you mean? The letter is only used twice, as per the specs. \$\endgroup\$
    – Josh
    Jan 17, 2014 at 16:37
  • 5
    \$\begingroup\$ @AdamSpeight ... which is literally the same. \$\endgroup\$
    – VisioN
    Jan 17, 2014 at 16:42
  • 4
    \$\begingroup\$ I think you mean a character should not appear more than twice, that is, it should not be repeated more than once. \$\endgroup\$ Jan 17, 2014 at 18:15
  • 58
    \$\begingroup\$ I guess brainfuck is out of the question... \$\endgroup\$
    – jub0bs
    Jan 17, 2014 at 18:26

70 Answers 70

1 2

PHP I am amazed at how many people give invalid answers without mentioning they are. My attempt, only reusing o" characters twice.

<?Php EchO "Hello wor\154d!";

Edit: fixed thanks to @FireFly: i understood to use each character once. This is no challenge anymore.

  • 1
    \$\begingroup\$ Wouldn't changing the \X6C into l make it completely valid? I only see one other l in there. \$\endgroup\$
    – FireFly
    Jan 23, 2014 at 10:50

JavaScript (52 characters)

alert(['He\x6C\x6Co world!'][(!1,0)-0], +-1+"Hadtw")

Each character is used 2 times, and it doesn't use any comments!

Edit: I've just posted the same answer here.


Active Server Pages (Classic ASP):

Hel<%REspOnsE.wRite Chr((0<0>-.6&"!")+&H6C+h-dinptO)
%>o world!

Each character is used twice!

To run it, you'll need a web server running IIS.

Save it in the site root with a ".asp" extension, make a HTTP request to the server, and you'll see that the response text is exactly "Hello world!" and a new line:

Hello world!

Edit: You could also use this smaller code:

Hel<%= Chr((0<0>we=6&"!")+&H6C+hd)
%>o world!

Or this:

Hel<%= CHr((0<1>wedC=8&"!&")++108)
%>o world!



main(){printf("He%clo world!%c",154,10);}
  • \$\begingroup\$ Doesn't work in general: codepad.org/O09aQhCe - on what platform does character code 186 give you 'll' ? \$\endgroup\$
    – Paul R
    Jan 18, 2014 at 10:33
  • \$\begingroup\$ In MS-DOS (code page 437 and similar) character with code 186 is double vertical line, used for drawing frames. \$\endgroup\$
    – AMK
    Jan 18, 2014 at 12:22
  • 1
    \$\begingroup\$ It's 38 chars. You missed '!'. Besides, the two vertical bars are not two L's \$\endgroup\$ Jan 19, 2014 at 2:06
  • \$\begingroup\$ It produces this output: He||o world! I'm using code blocks \$\endgroup\$
    – Mohammad
    Jan 19, 2014 at 9:43
  • \$\begingroup\$ Without ending '\n' this answer contains 35 chars. And output looks wery similar to Hello world!. But this answer may be wroted shorter as main(){puts("He║o world!");} \$\endgroup\$
    – AMK
    Jan 19, 2014 at 18:52

JavaScript 35

With inspiration from @VisioN


Tcl, 21 bytes

puts Hello\ wor\x6cd!

Try it online!



?@H[1]+@e[!0];CHR$(108);"lo world!

Another solution:

CLS?"He__o world!
LOCATE 2,0?@l[1]*2

In C. Choose one of these.

My favourite (crazy but compact in memory):

#include <stdint.h>
printf("%s", (char*)(int32_t[]){1819043144,1870078063,6581362});

For those who like big numbers:

printf("%s", (char*)(int64_t[]){8031924123371070792,43509902450});

Or here the more descriptive versions:

printf("%s", (char*)(int32_t[]){0x6c6c6548,0x6f77206f,0x646c72});
printf("%s", (char*)(int64_t[]){0x6f77206f6c6c6548,0x0a21646c72});

char map:

H  e  l  l     o     w  o     r  l  d  !     <LF>
48 65 6c 6c    6f 20 77 6f    72 6c 64 21    0a
(remember to swap big/little endian bytes when composing)

Btw: why there is no 128 bit integer in C?

printf("%s", (char*)(int128_t[]){0x0a21646c726f77206f6c6c6548});
printf("%s", (char*)(int128_t[]){802616035175250124568770929992}); // string uses only 100 of 128 bits
  • 2
    \$\begingroup\$ These don't met the requirements as some characters are used more than twice. Eg ( ) 0 1 2 9 etc etc \$\endgroup\$ Jan 17, 2014 at 22:50
  • 1
    \$\begingroup\$ When I look at the example in the question, I see print("He%so world!"%(2*'l')) which is 1p 2r 1i 1n 1t 2( 2" 1H 1e 2% etc. Even when I focus to the string I still see 2 o's, so why should my answer follow the rules when the question doesn't? ;-) \$\endgroup\$ Jan 17, 2014 at 22:57
  • \$\begingroup\$ printf("%s", (char*)(int32_t[]){1819043144,1870078063,6581362}); ( x 3, ) x 3, 1 x 5, 3 x 3, 4 x 4, 6 x 3, 8 x 4 \$\endgroup\$ Jan 17, 2014 at 23:08
  • \$\begingroup\$ Ok, I see. I misunderstood the specs. But I'm not the only one, when I look at the bash + ruby solutions of SztupY and the solution of cnst \$\endgroup\$ Jan 18, 2014 at 0:11
  • 1
    \$\begingroup\$ Just because someone else didn't follow the rules doesn't justify you. \$\endgroup\$
    – Dozer789
    Jan 18, 2014 at 19:11

AWK and echo

EDIT: fix the extra o's following the note. (thanks ProgramFOX)

echo He: | awk -F: '{print $1,Q,"\157 Wor",Q}' OFS=l ORS=d\!

and thanks awk which give me the option to say "-F" instead of "IFS=" (:-)

  • 3
    \$\begingroup\$ There are too many spaces, too. after echo, after He:, after |, and so on. \$\endgroup\$
    – Vereos
    Jan 21, 2014 at 8:33


Okay I found this on SO, it doesn't output a big H

Rare sequence of random stream of digits for 2 specific seeds.
Probably fixed out by brute forcing
One of the SO solutions also include a brute forcer to make your own sequences.

System.out.println(randomString(-229985452) + " " + randomString(-147909649) + "!");

And randomString() looks like this

public static String randomString(int i)
    Random ran = new Random(i);
    StringBuilder sb = new StringBuilder();
    for (int n = 0; ; n++)
        int k = ran.nextInt(27);
        if (k == 0)

        sb.append((char)('`' + k));

    return sb.toString();

Source: https://stackoverflow.com/questions/15182496/why-does-this-code-print-hello-world

  • 5
    \$\begingroup\$ And this meets the specs, how? I can easily count 3 S's, 3 spaces, 3 2's, etc. \$\endgroup\$
    – Justin
    Jan 18, 2014 at 8:05
1 2

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