New articles - OurBigBook.com

Moore matrix by

Wikipedia Bot 0  1970-01-01

Hemoglobin by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

Stefan Thomas by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

www.nytimes.com/2021/01/12/technology/bitcoin-passwords-wallets-fortunes.html

As for his lost password and inaccessible Bitcoin, Mr. Thomas has put the IronKey in a secure facility - he won’t say where - in case cryptographers come up with new ways of cracking complex passwords. Keeping it far away helps him try not to think about it, he said.

“I would just lay in bed and think about it," Mr. Thomas said.

What is Bitcoin? (v1) by WeUseCoins (2011)

Source. This is the video that Stefan Thomas as paid 7,002 Bitcoins to make back in 2011.

Amateur telescope vendor by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

Albert Victor Bäcklund by

Wikipedia Bot 0  1970-01-01

The best articles by Ciro Santilli by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

These are the best articles ever authored by Ciro Santilli, most of them in the format of Stack Overflow answers.

Ciro posts update about new articles on his Twitter accounts.

A chronological list of all articles is also kept at: Section "Updates".

Some random generally less technical in-tree essays will be present at: Section "Essays by Ciro Santilli".

Trended on Hacker News:
- CIA 2010 covert communication websites on 2023-06-11. 190 points, a mild success.
- x86 Bare Metal Examples on 2019-03-19. 513 points. The third time something related to that repo trends. Hacker news people really like that repo!
  - again 2020-06-27 (archive). 200 points, repository traffic jumped from 25 daily unique visitors to 4.6k unique visitors on the day
- How to run a program without an operating system? on 2018-11-26 (archive). 394 points. Covers x86 and ARM
- ELF Hello World Tutorial on 2017-05-17 (archive). 334 points.
- x86 Paging Tutorial on 2017-03-02. Number 1 Google search result for "x86 Paging" in 2017-08. 142 points.
  Figure 1.
  BIOS bare metal hello world running on a Lenovo ThinkPad T430
  . Source.
x86 assembly
- What does "multicore" assembly language look like?
- What is the function of the push / pop instructions used on registers in x86 assembly? Going down to memory spills, register allocation and graph coloring.
Linux kernel
QEMU
gcc and Binutils:
- How do linkers and address relocation works?
- What is incremental linking or partial linking?
- GOLD (-fuse-ld=gold) linker vs the traditional GNU ld and LLVM ldd
- What is the -fPIE option for position-independent executables in GCC and ld? Concrete examples by running program through GDB twice, and an assembly hello world with absolute vs PC relative load.
- How many GCC optimization levels are there?
- Why does GCC create a shared object instead of an executable binary according to file?
C/C++: almost all of those fall into "disassemble all the things" category. Ciro also does "standards dissection" and "a new version of the standard is out" answers, but those are boring:
- What does "static" mean in a C program?
- In C++ source, what is the effect of extern "C"?
- Char array vs Char Pointer in C
- How to compile glibc from source and use it?
- When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used?
- What exactly is std::atomic in C++?. This answer was originally more appropriately entitled "Let's disassemble some stuff", and got three downvotes, so Ciro changed it to a more professional title, and it started getting upvotes. People judge books by their covers.
- notmain.o 0000000000000000 0000000000000017 W MyTemplate<int>::f(int) main.o 0000000000000000 0000000000000017 W MyTemplate<int>::f(int)
  Code 1.
  nm outputs showing that objects are redefined multiple times across files if you don't use template instantiation properly
  . From: What is explicit template instantiation in C++ and when to use it?

IEEE 754

What is difference between quiet NaN and signaling NaN?
In Java, what does NaN mean?

Without subnormals:

          +---+---+-------+---------------+-------------------------------+
exponent  | ? | 0 |   1   |       2       |               3               |
          +---+---+-------+---------------+-------------------------------+
          |   |   |       |               |                               |
          v   v   v       v               v                               v
          -----------------------------------------------------------------
floats    *    **** * * * *   *   *   *   *       *       *       *       *
          -----------------------------------------------------------------
          ^   ^   ^       ^               ^                               ^
          |   |   |       |               |                               |
          0   |   2^-126  2^-125          2^-124                          2^-123
              |
              2^-127

With subnormals:

          +-------+-------+---------------+-------------------------------+
exponent  |   0   |   1   |       2       |               3               |
          +-------+-------+---------------+-------------------------------+
          |       |       |               |                               |
          v       v       v               v                               v
          -----------------------------------------------------------------
floats    * * * * * * * * *   *   *   *   *       *       *       *       *
          -----------------------------------------------------------------
          ^   ^   ^       ^               ^                               ^
          |   |   |       |               |                               |
          0   |   2^-126  2^-125          2^-124                          2^-123
              |
              2^-127

Code 2.

Visualization of subnormal floating point numbers vs what IEEE 754 would look like without them

. From: What is a subnormal floating point number?

Computer science
- Algorithms
  - Figure 5.
    Average insertion time into heaps, binary search tree and hash maps of the C++ standard library
    . Source. From: Heap vs Binary Search Tree (BST)
- Is it necessary for NP problems to be decision problems?
- Polynomial time and exponential time. Answered focusing on the definition of "exponential time".
- What is the smallest Turing machine where it is unknown if it halts or not?. Answer focusing on "blank tape" initial condition only. Large parts of it are summarizing the Busy Beaver Challenge, but some additions were made.

Git

  | 0           | 4            | 8           | C              |
  |-------------|--------------|-------------|----------------|
0 | DIRC        | Version      | File count  | ctime       ...| 0
  | ...         | mtime                      | device         |
2 | inode       | mode         | UID         | GID            | 2
  | File size   | Entry SHA-1                              ...|
4 | ...                        | Flags       | Index SHA-1 ...| 4
  | ...                                                       |

Code 3.

ASCII art depicting the binary file format of the Git index file

. From: What does the git index contain EXACTLY?

tree {tree_sha}
{parents}
author {author_name} <{author_email}> {author_date_seconds} {author_date_timezone}
committer {committer_name} <{committer_email}> {committer_date_seconds} {committer_date_timezone}

{commit message}

Code 4.

Description of the Git commit object binary data structure

. From: What is the file format of a git commit object data structure?

How do I clone a subdirectory only of a Git repository?

Python
- What is the difference between old style and new style classes in Python?
- What is a mixin in Python, and why are they useful?
- What are the differences between threads and processes in Python?
  Figure 6.
  Python Threads vs Processes with 8 hyperthreads
  . Source.
Web technology
- What does enctype='multipart/form-data' mean?
- JavaScript
  - How does JavaScript .prototype work?
  - What is the difference between .prop() vs .attr() in JavaScript?
OpenGL
- Figure 7.
  OpenGL rendering output dumped to a GIF file
  . Source. From: How to use GLUT/OpenGL to render to a file?
- Figure 8.
  Example of a texture atlas containing glyphs
  . Source.
  Image by Nicolas P. Rougier, author of Freetype GL.
  Used on Ciro Santilli's answer: How to draw text using only OpenGL methods?
- Figure 9.
  OpenGL glFrustrum vs glOrtho
  . Source. From: How to use glOrtho() in OpenGL?
- What are shaders in OpenGL?
- Why do we use 4x4 matrices to transform things in 3D?
- Figure 10.
  Sinusoidal circular wave heatmap generated with an OpenGL shader at 60 FPS on SDL
  . Source.
  From: Is it possible to build a heatmap from point data at 60 times per second?
  Compared CPU vs GPU shaders.
- Image Processing with GLSL shaders? Compared the CPU and GPU for a simple blur algorithm.
  Figure 11. Source.
  Video 1.
  OpenGL GPU GLSL fragment shader real time v4l2 Linux webcam computer vision box blur vs CPU
  . Source.
Node.js
- What's the difference between dependencies, devDependencies and peerDependencies in npm package.json file?
Ruby on Rails
- What is the difference between +<%+, +<%=+, +<%#+ and +-%>+ in ERB in Rails?
POSIX
- What is POSIX? Huge classified overview of the most important things that POSIX specifies.

Systems programming

What do the terms "CPU bound" and "I/O bound" mean?
Figure 12.
Plot of "real", "user" and "sys" mean times of the output of time for CPU-bound workload with 8 threads
. Source. From: What do 'real', 'user' and 'sys' mean in the output of time?

+--------+                  +------------+       +------+
| device |>---------------->| function 0 |>----->| BAR0 |
|        |                  |            |       +------+
|        |>------------+    |            |
|        |             |    |            |       +------+
   ...        ...      |    |            |>----->| BAR1 |
|        |             |    |            |       +------+
|        |>--------+   |    |            |
+--------+         |   |         ...        ...    ...
                   |   |    |            |
                   |   |    |            |       +------+
                   |   |    |            |>----->| BAR5 |
                   |   |    +------------+       +------+
                   |   |
                   |   |
                   |   |    +------------+       +------+
                   |   +--->| function 1 |>----->| BAR0 |
                   |        |            |       +------+
                   |        |            |
                   |        |            |       +------+
                   |        |            |>----->| BAR1 |
                   |        |            |       +------+
                   |        |            |
                   |             ...        ...    ...
                   |        |            |
                   |        |            |       +------+
                   |        |            |>----->| BAR5 |
                   |        +------------+       +------+
                   |
                   |
                   |             ...
                   |
                   |
                   |        +------------+       +------+
                   +------->| function 7 |>----->| BAR0 |
                            |            |       +------+
                            |            |
                            |            |       +------+
                            |            |>----->| BAR1 |
                            |            |       +------+
                            |            |
                                 ...        ...    ...
                            |            |
                            |            |       +------+
                            |            |>----->| BAR5 |
                            +------------+       +------+

Code 5.

Logical struture PCIe device, functions and BARs

. From: What is the Base Address Register (BAR) in PCIe?

Electronics
- Raspberry Pi
  - Figure 13.
    Raspberry Pi 2 directly connected to a laptop with an Ethernet cable
    . Image from answer to: How to hook up a Raspberry Pi via Ethernet to a laptop without a router?
    Figure 14.
    Raspberry Pi 2 connected to a laptop with an USB UART adapter
    . Image from answer to: How to hook up a Raspberry Pi via Ethernet to a laptop without a router?
    Figure 15.
    Raspberry Pi OS being emulated on QEMU 2.5.0 on Ubuntu 16.04 with a modified kernel
    . Image from answer to: How to emulate the Raspberry Pi 2 on QEMU?
    Figure 16.
    Bare metal LED blinker program running on a Raspberry Pi 2
    . Image from answer to: How to run a C program with no OS on the Raspberry Pi?
Computer security
- Why is the same origin policy so important?
Media
- Video 2.
  Canon in D in C
  . Source.
  From: How is audio represented with numbers in computers?.
  The original question was deleted, lol...: How to programmatically synthesize music?
- How to resize a picture using ffmpeg's sws_scale()?
- Is there any decent speech recognition software for Linux? ran a few examples manually on vosk-api and compared to ground truth.
Eclipse
- How to set up the Eclipse for remote C debugging with gdbserver?
Computer hardware
- Are there good open source standard cell libraries to learn IC synthesis with EDA tools?
Scientific visualization software
- Figure 17.
  VisIt zoom in 10 million straight line plot with some manually marked points
  . Source. From: Section "Survey of open source interactive plotting software with a 10 million point scatter plot benchmark by Ciro Santilli"
Numerical analysis
- Video 3.
  Real-time heat equation OpenGL visualization with interactive mouse cursor using relaxation method by Ciro Santilli (2016)
  Source.
Computational physics
- Figure 18.
  gnuplot plot of the y position of a sphere bouncing on a plane simulated in Bullet Physics
  . Source. From: What is the simplest collision example possible in a Bullet Physics simulation?
Register transfer level languages like Verilog and VHDL
- Verilog:
  Figure 19.
  Interacgive ASDF-controlled demo with core logic written in Verilog using Verilator
  .
  From: Is it possible to do interactive user input and output simulation in VHDL or Verilog?
  See also: Section "Verilator interactive example"
Android
- Figure 20. Source. From: How to compile the Android AOSP kernel and test it with the Android Emulator?
- Video 4.
  Android screen showing live on an Ubuntu laptop through ADB
  . Source. From: How to see the Android screen live on an Ubuntu desktop through ADB?
Debugging
Program optimization
- What is tail call optimization?
- Figure 21.
  gprof2dot image generated from the gprof data of a simple test program
  . Source.
  From: How can I profile C++ code running on Linux?
  The answer compares gprof, valgrind callgrind, perf and gperftools on a single simple executable.
Data
- Figure 22.
  Mathematics dump of Wikipedia CatTree
  . Source. In this project, Ciro Santilli explored extracting the category and article tree out of the Wikipedia dumps.
Mathematics
- Figure 23.
  Diagram of the fundamental theorem on homomorphisms by Ciro Santilli (2020)
  
  Shows the relationship between group homomorphisms and normal subgroups.
  From: What is the intuition behind normal subgroups?
- Section "Formalization of mathematics": some early thoughts that could be expanded. Ciro almost had a stroke when he understood this stuff in his teens.
- Figure 24.
  Simple example of the Discrete Fourier transform
  . Source. That was missing from Wikipedia page: en.wikipedia.org/wiki/Discrete_Fourier_transform!
Network programming
- How to make an HTTP get request in C without libcurl?
Physics
- What is the difference between plutonium and uranium?
- Figure 25.
  Spacetime diagram illustrating how faster-than-light travel implies time travel
  . From: Does faster than light travel imply travelling back in time?
Biology
- Figure 26.
  Top view of an open Oxford Nanopore MinION
  . Source. From: Section "How to use an Oxford Nanopore MinION to extract DNA from river water and determine which bacteria live in it"
- Figure 27.
  Mass fractions in a minimal growth medium vs an amino acid cut in a simulation of the E. Coli Whole Cell Model by Covert Lab
  . Source. From: Section "E. Coli Whole Cell Model by Covert Lab"
Quantum computing
- Section "Quantum computing is just matrix multiplication"
- Figure 28.
  Visualization of the continuous deformation of states as we walk around the Bloch sphere represented as photon polarization arrows
  . From: Understanding the Bloch sphere.
Bitcoin
- Section "Cool data embedded in the Bitcoin blockchain"
GIMP
- Figure 29.
  GIMP screenshot part of how to combine two images side-by-side in GIMP?
  .
Home DIY
- Figure 30.
  Total_Blackout_Cassette_Roller_Blind_With_Curtains.
  Source. From: Section "How to blackout your window without drilling"
China
- What would happen if I walked around Beijing with a t-shirt that said "freedom of speech is pretty great"?

Feces by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

Stephen Hawking by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

While learning black-hole stuff is not on top of Ciro Santilli's priorities, Hawking's spirit is to be admired.

To never give up even when everything seems lost, and still have a sense of humour is respectable.

An ex-physicist colleague who had met Hawking told an anecdote. Hawking was around in the department one day, they said hi and all. But then Hawking wanted to tell a joke. It took like 5 minutes of typing, and you can imagine that things were pretty awkward and the joke's timing was "a bit off". But Hawking did tell the joke nonetheless.

This is also suggested in the The Theory of Everything (2014) film, and therefore likely the biographies.

Steven H. Simon by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

www.youtube.com/@stevensimon2285

Steve Jobs quote on saving lives with a faster boot by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

www.folklore.org/StoryView.py?story=Saving_Lives.txt

This idea also comes up in other sources of course.

Margin Call (2011) bridge scene

. Source.

Star Wars by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

Star outside the Milky Way by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

It is not possible to see stars outside of the Milky Way by naked eye.

With telescopes however, it is possible. www.quora.com/Can-we-distinguish-individual-stars-in-other-galaxies-or-would-it-be-equivalent-to-say-we-know-there-are-other-forests-of-stars-galaxies-but-we-cant-tell-the-individual-trees-stars-What-is-the-farthest-individual/answer/Jerzy-Micha%C5%82-Pawlak contains an amazing answer that mentions two special cases of the furthest ones:

gravitational lensing observation
a star that is far but visible because its light is reflected by a nearby nebulae

But what we can definitely see are globular clusters of galaxies. E.g. the article en.wikipedia.org/wiki/Messier_87 basically gauges the size of galaxies by the number of globular clusters that they contain.

OurBigBook.com / Alternatives by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

These are websites that offer somewhat overlapping services, many of which served inspirations, and why we think something different is needed to achieve our goals.

Notably, OurBigBook is the result of Ciro Santilli's experiences with:

Wikipedia
GitHub
Stack Exchange (or as non techies might point out, Urban Dictionary, or Quora before it was such an incomprehensible shitshow)

OurBigBook could be seen as a cross between those three websites.

Quick mentions:

handwiki.org/wiki/HandWiki:About: technically the same as Wikipedia, but with more aligned moderation policies
ecotext.co/ similar goals. Their website seems quite broken now though as of 2021, can't see text properly. Crunchbase entry: www.crunchbase.com/organization/ecotext says they are from Durham, New Hampshire, United States. Cannot see how to publish, curated material only? Twitter: twitter.com/ecotextinc?lang=en One of the founders: twitter.com/BigNel_21 | www.linkedin.com/in/ecotextnelsonthomas/. Their LinkedIn: www.linkedin.com/company/ecotext/people/
fiveable.me/ bad: separates students and teachers, as a student I don't see where to create my content. Good: focus on teaching university level stuff to people outside of university via Advanced Placement. Bad: Lots of video content. Bad: Can't see the issue tracker attached to each page.
LessWrong: their website system does have some similar feature sets to what we want. Reputation, Q&A sections, links between articles most likely, sort by upvote everywhere.
crowdpub.org collaborative writing website, somehow goes to paragraph level, TODO how they reconcile different authors? Closed beta as of writing, so hard to be sure. From quick presentation on beta website, appears to attempt to share revenue to authors proportionally to the size of their contribution. Some blockchain-based reputation. Meh.
TODO migrate all from: github.com/booktree/booktree/blob/master/alternatives.md
studynotes.ie/. Admin approval on everything. No ToC. Fixed tag list for university entry exams topics.
mindstone.com: there appears to be no sharing focus? File upload basesd? Not sure.
EverybodyWiki
looking for open source Confluence-alternatives is an interesting way to go:
- lists:
  - opensource.com/article/20/9/open-source-alternatives-confluence
  - www.nuclino.com/alternatives/confluence-alternative#ynaw
- BookStack:
  - fixed 3-level page hierarchy
  - writen in PHP
  - Markdown support: www.bookstackapp.com/docs/user/markdown-editor/
  - no source-level import-export apparently: www.bookstackapp.com/docs/admin/backup-restore/, youtu.be/WUvtzJfCAKE?t=904
  - WYSIWYG: www.bookstackapp.com/docs/user/wysiwyg-editor/ via TinyMCE
  - page content repeating: www.bookstackapp.com/docs/user/reusing-page-content/ (will be useful for course modelling)
github.com/shuding/nextra converts Markdown links to Next.js links. We should look into how it works.
zettelkasten.de/the-archive/ "The Archive" from zettelkasten.de/. Closed source. By German software engineer Christian Tietze twitter.com/ctietze?lang=en
LLM generated wiki e.g.:
- Kinnu
docs.tigyog.app/cli beautiful website, but doesn't achieve much. Has a Markdown upload mechanism. Ah, those newbs who think the average user will care about markup upload to DB... Oh, wait...
www.stuvia.com/en-gb/school/uk/oxford-university/physics. PDF uploads. In theory you have to own copyright: www.stuvia.com/en-gb/copyright/guidelines but it feels unlikely that most material was uploaded by the copyright owners. If those people are up, then why can't we? Maybe... Registred in the UK. People: some Dutch dudes:
- www.linkedin.com/in/jaapvannes
- www.linkedin.com/in/hugo-kuijzer-bb81a625
Project Xanadu: crazy overlaps, though that project is vaporware apparently?
Administrators of Project Xanadu have declared it superior to the World Wide Web, with the mission statement: "Today's popular software simulates paper. The World Wide Web (another imitation of paper) trivialises our original hypertext model with one-way ever-breaking links and no management of version or contents.

Static website-only alternatives:

quarto.org/
- Links have forced file scope:^[ref]
  [about](about.qmd) [about](about.qmd#section)
- WYSIWYG via RStudio
vitepress.dev. vitepress.dev/guide/markdown unmanaged internal links. Sample website: wiki.nikiv.dev/.

Conceptual:

The Final Encyclopedia: science fiction concept, but the name was reused by Paul Allen in a research project
second brain
collective intelligence

TODO:

pressbooks.directory/

Internet search algorithms by

Wikipedia Bot 0  1970-01-01

Single electron double slit experiment by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

Electron Interference by the Italian National Research Council (1976)

Source.

Institutional video about the 1974 single electron experiment by Merli, Missiroli, Pozzi from the University of Bologna.

Uses an electron biprism as in electron holography inside a transmission electron microscope.

Shows them manually making the biprism by drawing a fine glass wire and coating it with gold.

Then actually show the result live on a television screen, where you see the interference patterns only at higher electron currents, and then on photographic film.

This was elected "the most beautiful experiment" by readers of Physics World in 2002.

Accompanying website: l-esperimento-piu-bello-della-fisica.bo.imm.cnr.it/english/index.html.

Italian title: "Interferenza di elettroni". Goddammit, those Italian cinematographers can make even physics look exciting!

Cheap oscilloscope by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

www.reddit.com/r/ECE/comments/jqfv4f/what_is_the_cheapest_oscilloscope_available_and/

DIY Oscilloscope Kit (20$) VS Regular DS Oscilloscope (400$) by Great Scott (2016)

Source.

Video 2.

Hantek 6022BE Review by Adrian's Digital Basement (2022)

Source.

RNA half-life prediction by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

Exponential search by

Wikipedia Bot 0  1970-01-01

Standard Model by

Ciro Santilli 35  Updated 2025-04-24  +Created 1970-01-01

As of 2019, the more formal name for particle physics, which is notably missing general relativity to achieve the theory of everything.

cds.cern.ch/record/799984/files/0401010.pdf The Making of the Standard Model by Steven Weinberg mentions three crucial elements that made up the standard model post earlier less generalized quantum electrodynamics understandings

 Pinned article: ourbigbook/introduction-to-the-ourbigbook-project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.

Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!