[barbegal]

I was confused as to how you could represent a bootable CD image in printable characters. It turns out that you can't. This is a tweet of a perl script which creates a cd.iso file that you can then boot from. The perl script significantly decompresses the data in the tweet.

That said, this is a playable game in around 60 bytes of actual data which is impressive.

[mirimir]

I'm reminded of the RSA in Perl "weapon" t-shirt :)

https://upload.wikimedia.org/wikipedia/commons/9/96/Munition...

[raphlinus]

Machine readable as well as machine washable[0]!

[0]: http://cypherpunks.venona.com/archive/1995/10/msg00317.html

[cheeze]

Man that shirt is awesome... But man I would never wear that shirt as that looks like the crown jewel of any neckbeards collection

[OscarCunningham]

It sounds like you've been trained to hate something that you actually love. That's kind of sad. Couldn't you just wear the awesome shirt while avoiding the negative aspects of neckbeards?

[garaetjjte]

Not CD images, but there is DOS C compiler generating executables with only printable characters (and also no self-modifying code that could contain non-printable characters)

http://www.cs.cmu.edu/~tom7/abc/paper.txt (view in monospace font, 160 character lines)

[gerdesj]

That said, this is a playable game in around 60 bytes of actual data which is impressive.

.. and way smaller than your comment .

[makomk]

It's pretty light compression from what I can tell - basically just squashing down runs of nulls to a single count.

[wtmcc]

The compression is basic run-length encoding, leveraging the Perl repetition operator (x), and the property of the Perl print/say functions that they concat items passed in a list before writing to STDOUT.

https://en.wikipedia.org/wiki/Run-length_encoding

https://perldoc.perl.org/perlop.html#Multiplicative-Operator...

https://perldoc.perl.org/functions/say.html

https://perldoc.perl.org/functions/print.html

[lucb1e]

I tried xz -9 on it and found, to my surprise, that it was actually longer than RLE!

Then I tried gzip -9, because perhaps that has a smaller header? Yup, saved a few bytes, now it's about the same size. Finally, I remembered that bzip2 does a lot better on text than gzip, and who knows, it might also have a shorter header than xz. Again, a few more bytes saved! Down to 223, where the original is 249 bytes (including the 'say' part but excluding the unnecessary delimiting apostrophes or the rest of the command).

[SlowRobotAhead]

Took me a second to figure out after looking at the assembly that it's possible because of base64.

[arcticbull]

Yeah, it's a really simple run-length encoded ISO expressed as a Perl script.

[pard68]

I looked at the that tweet for five or six minutes and was stumped. Now this makes more sense, thanks.

[0xcde4c3db]

Most of the "compression" is zero bytes due to fixed offsets of various things (e.g. the first 16 sectors of an ISO 9660 image are a "system area" not used by the actual file system).