Ciro Santilli @cirosantilli 37 

E-learning Updated 2025-07-16

See also: e-learning website.

E-learning websites must keep content free, only charge for certification Updated 2025-07-16

Charging for certification is fine. Creating exams and preventing cheating has a cost.

Another thing that is fine charging for is dedicated 1-to-1 tutor time. This is something Udacity is doing as of 2022.

www.investopedia.com/articles/investing/042815/how-coursera-works-makes-money.asp has a good mention:

MOOCs were first created by people with utopian visions for the internet. This means the idea for platforms like Coursera was likely conceived without a business plan in mind. Nonetheless, Coursera has managed to monetize its platform. It is worth noting, however, that monetization has lead to the effective elimination of the original MOOC idea, which is predicated on ideals like free and open access, as well as the building of online communities.
Coursera users must pay to engage with the material in a meaningful way and take courses for individualistic purposes. This has been a consistent trend among all major online education platforms.

and it links to: www.freecodecamp.org/news/massive-open-online-courses-started-out-completely-free-but-where-are-they-now-1dd1020f59/, very good article!

That is a fundamental guiding principle of OurBigBook.com. The educational content must be licensed CC BY-SA!

Perhaps the most reliable way of reaching this state is E-learning websites must allow students to create learning content.

Bibliography:

academia.stackexchange.com/questions/86179/is-it-financially-worth-it-to-teach-a-mooc-e-g-coursera Is it financially worth it to teach a MOOC (e.g. Coursera)?
www.classcentral.com/about amazing, they can make money just from ads! I wouldn't expect that they could scale like TripAdvisor, because travelling means very local knowledge, I would expect there to be much fewer MOOCs and for them to be more easily findable on Google. Good thing though, this website.

Electrical impedance Updated 2025-07-16

Ciro Santilli distinctly remembers being taught that at basic electrical engineering school during Ciro Santilli's undergrad studies at the University of São Paulo.

It really allows you to do alternating current calculations much as you'd do DC calculations with resistors, quite poweful. It must have been all the rage in the 1950s.

Electromagnetism Updated 2025-07-16

As of the 20th century, this can be described well as "the phenomena described by Maxwell's equations".

Back through its history however, that was not at all clear. This highlights how big of an achievement Maxwell's equations are.

Electronic component Updated 2025-07-16

Open Circuits book interview by CuriousMarc (2022)

Source.

Electronic money Updated 2025-07-16

Our minimal definition of "electronic money" is the following.

Instead of creating legal tender such as Dollars as banknotes or transactions in some complex obscure banking system, the government offers an official simple centralized API that represents it instead.

Each citizen or legal entity has an account there, and transfers between registered users are just simple API calls.

So for example you would e able to put all your money in the government account instead of using useless banks. And then you would invest it as you want with the investment company of your choice, without tying the "my money is here" with "this is the best investment" aspects of banks.

Java (programming language) Updated 2025-07-16

Java is good.

Its boilerplate requirement is a pain, but the design is otherwise very clean.

But its ecosystem sucks.

The development process is rather closed, the issue tracker obscure.

And above all, Google LLC v. Oracle America, Inc. killed everybody's trust in it once and for all. Thanks Oracle.

Java for the Haters in 100 Seconds by Fireship (2022)

Source.

Electronic oscillator Updated 2025-07-16

Something where DC voltage comes in, and a periodic voltage comes out.

Oscillators: RC, LC, Crystal by GreatScott! (2015)

Source. Good video. Contains actual breadboard experiments on oscilloscope and circuit diagrams

youtu.be/eYVOdlK15Og?t=66 RC oscillator on breadboard. Produces rectangular wave. Mentions popular integrated circuit that does it: 555 timer IC.
youtu.be/eYVOdlK15Og?t=175 LC oscillators allows for higher frequencies. Produces sinusoidal output on MHz range. Uses an amplifier to feed back into input and maintain same voltage. Hard to make reliably on breadboard.
youtu.be/eYVOdlK15Og?t=315 crystal oscillator. Mentions it acts like an LC oscillators. Shows and equivalent model. Wish he had talked more about them. You need support components around it: similarly to the LC case, the amplifier is generally not packaged in.

JavaScript Updated 2025-07-16

The language all browsers converted to as of 2019, and therefore the easiest one to distribute and most widely implemented programming language.

Hopefully will be killed by WebAssembly one day.

Because JavaScript is a relatively crap/ad-hoc language, it ended up some decent tooling to make up for that, e.g. stuff like linting via ESLint and reformatting through Prettier is much more widespread than in other languages.

JavaScript data structure are also quite a bit anemic, which makes libraries such as lodash incredibly popular. But most of that stuff should be in the stdlib.

Our JavaScript examples can be found at:

Node.js example: examples that don't interact with any browser feature. We are just testing those on the CLI which is much more convenient.
JavaScript browser example: examples that interact with browser-specific features, notably the DOM

JavaScript browser example Updated 2025-07-16

js/confirm-close.html: stackoverflow.com/questions/7317273/warn-user-before-leaving-web-page-with-unsaved-changes
web-cheat/js-image-load.html: load an image from JavaScript dynamically: stackoverflow.com/questions/226847/what-is-the-best-javascript-code-to-create-an-img-element
web-cheat/js-image-load-viewport.html: load an image from JavaScript dynamically when it would become visible on the viewport: stackoverflow.com/questions/2321907/how-do-you-make-images-load-only-when-they-are-in-the-viewport
html/img-load-lazy.html: stackoverflow.com/questions/2321907/how-do-you-make-images-load-lazily-only-when-they-are-in-the-viewport/57389607#57389607
web-cheat/esm.html: ESM modules
- web-cheat/esm1.js
- web-cheat/esm2.js
js/keydown.html: stackoverflow.com/questions/16006583/capturing-ctrlz-key-combination-in-javascript

External libraries

Electronic voting Updated 2025-07-16

This is a must if the people want to regain control of their society from apathetic politicians.

I would also increase voter percentage due to convenience, and reduce the weight of voting fraud cases, as everyone would be able to check that their own vote was counted correctly.

And then, we would be able to have referendums for basically any important decision being made. No need to go out on the streets and waste your time in a mass protest! Just vote!

It is possible to implement anonymous electronic voting with ring signatures, an algorithm also used by Monero, an anonymity focused cryptocurrency, as mentioned e.g. on this 2004 paper eprint.iacr.org/2004/281.pdf. The system can be set in a way such that you can only deanonymize someone if everyone else, or a very large number of people, conspire against that person.

The same system could also be used to setup forums where only citizens of the country could comment and propose changes and vote on them.

With electronic voting, we could have a system where you can let someone you trust vote for you automatically, or vote automatically for certain subjects alone, a bit like we do by electing senators. But then you would also be able to override specific votes if you wanted to.

In this system therefore, anyone who can proxy vote has to have their vote public, and placed in a decent website that shows clearly who voted for what.

www.vote-coin.com/ allows you to delegate your voting power to someone else, that's perfect!

Electroweak interaction Updated 2025-07-16

Electroweak Theory and the Origin of the Fundamental Forces by PBS Space Time (2020)

Source. Unsatisfactory, as usual.

Elementary charge Updated 2025-07-16

Experiments to measure it:

oil drop experiment

The 2019 redefinition of the SI base units defines it precisely and uses it as a measure of charge: en.wikipedia.org/wiki/2019_redefinition_of_the_SI_base_units#Ampere

Jazz fusion Updated 2025-07-16

Ciro Santilli's favorite music genre.

Ciro's 2020 perfect Friday evening: jazz fusion + study quantum field theory on an Amazon Kindle. Ahhhhhh.

ELF Hello World Tutorial / Executable hd Updated 2025-07-16

Running:

hd hello_world.out

gives:

00000000  7f 45 4c 46 02 01 01 00  00 00 00 00 00 00 00 00  |.ELF............|
00000010  02 00 3e 00 01 00 00 00  b0 00 40 00 00 00 00 00  |..>.......@.....|
00000020  40 00 00 00 00 00 00 00  10 01 00 00 00 00 00 00  |@...............|
00000030  00 00 00 00 40 00 38 00  02 00 40 00 06 00 03 00  |....@.8...@.....|
00000040  01 00 00 00 05 00 00 00  00 00 00 00 00 00 00 00  |................|
00000050  00 00 40 00 00 00 00 00  00 00 40 00 00 00 00 00  |..@.......@.....|
00000060  d7 00 00 00 00 00 00 00  d7 00 00 00 00 00 00 00  |................|
00000070  00 00 20 00 00 00 00 00  01 00 00 00 06 00 00 00  |.. .............|
00000080  d8 00 00 00 00 00 00 00  d8 00 60 00 00 00 00 00  |..........`.....|
00000090  d8 00 60 00 00 00 00 00  0d 00 00 00 00 00 00 00  |..`.............|
000000a0  0d 00 00 00 00 00 00 00  00 00 20 00 00 00 00 00  |.......... .....|
000000b0  b8 01 00 00 00 bf 01 00  00 00 48 be d8 00 60 00  |..........H...`.|
000000c0  00 00 00 00 ba 0d 00 00  00 0f 05 b8 3c 00 00 00  |............<...|
000000d0  bf 00 00 00 00 0f 05 00  48 65 6c 6c 6f 20 77 6f  |........Hello wo|
000000e0  72 6c 64 21 0a 00 2e 73  79 6d 74 61 62 00 2e 73  |rld!...symtab..s|
000000f0  74 72 74 61 62 00 2e 73  68 73 74 72 74 61 62 00  |trtab..shstrtab.|
00000100  2e 74 65 78 74 00 2e 64  61 74 61 00 00 00 00 00  |.text..data.....|
00000110  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000150  1b 00 00 00 01 00 00 00  06 00 00 00 00 00 00 00  |................|
00000160  b0 00 40 00 00 00 00 00  b0 00 00 00 00 00 00 00  |..@.............|
00000170  27 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |'...............|
00000180  10 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000190  21 00 00 00 01 00 00 00  03 00 00 00 00 00 00 00  |!...............|
000001a0  d8 00 60 00 00 00 00 00  d8 00 00 00 00 00 00 00  |..`.............|
000001b0  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001c0  04 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001d0  11 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
000001e0  00 00 00 00 00 00 00 00  e5 00 00 00 00 00 00 00  |................|
000001f0  27 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |'...............|
00000200  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000210  01 00 00 00 02 00 00 00  00 00 00 00 00 00 00 00  |................|
00000220  00 00 00 00 00 00 00 00  90 02 00 00 00 00 00 00  |................|
00000230  08 01 00 00 00 00 00 00  05 00 00 00 07 00 00 00  |................|
00000240  08 00 00 00 00 00 00 00  18 00 00 00 00 00 00 00  |................|
00000250  09 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
00000260  00 00 00 00 00 00 00 00  98 03 00 00 00 00 00 00  |................|
00000270  4c 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |L...............|
00000280  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000290  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002a0  00 00 00 00 00 00 00 00  00 00 00 00 03 00 01 00  |................|
000002b0  b0 00 40 00 00 00 00 00  00 00 00 00 00 00 00 00  |..@.............|
000002c0  00 00 00 00 03 00 02 00  d8 00 60 00 00 00 00 00  |..........`.....|
000002d0  00 00 00 00 00 00 00 00  01 00 00 00 04 00 f1 ff  |................|
000002e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002f0  11 00 00 00 00 00 02 00  d8 00 60 00 00 00 00 00  |..........`.....|
00000300  00 00 00 00 00 00 00 00  1d 00 00 00 00 00 f1 ff  |................|
00000310  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000320  00 00 00 00 04 00 f1 ff  00 00 00 00 00 00 00 00  |................|
00000330  00 00 00 00 00 00 00 00  2d 00 00 00 10 00 01 00  |........-.......|
00000340  b0 00 40 00 00 00 00 00  00 00 00 00 00 00 00 00  |..@.............|
00000350  34 00 00 00 10 00 02 00  e5 00 60 00 00 00 00 00  |4.........`.....|
00000360  00 00 00 00 00 00 00 00  40 00 00 00 10 00 02 00  |........@.......|
00000370  e5 00 60 00 00 00 00 00  00 00 00 00 00 00 00 00  |..`.............|
00000380  47 00 00 00 10 00 02 00  e8 00 60 00 00 00 00 00  |G.........`.....|
00000390  00 00 00 00 00 00 00 00  00 68 65 6c 6c 6f 5f 77  |.........hello_w|
000003a0  6f 72 6c 64 2e 61 73 6d  00 68 65 6c 6c 6f 5f 77  |orld.asm.hello_w|
000003b0  6f 72 6c 64 00 68 65 6c  6c 6f 5f 77 6f 72 6c 64  |orld.hello_world|
000003c0  5f 6c 65 6e 00 5f 73 74  61 72 74 00 5f 5f 62 73  |_len._start.__bs|
000003d0  73 5f 73 74 61 72 74 00  5f 65 64 61 74 61 00 5f  |s_start._edata._|
000003e0  65 6e 64 00                                       |end.|
000003e4

ELF Hello World Tutorial / Generate the example Updated 2025-07-16

Let's break down a minimal runnable Linux x86-64 example:

hello_world.asm

section .data
    hello_world db "Hello world!", 10
    hello_world_len  equ $ - hello_world
section .text
    global _start
    _start:
        mov rax, 1
        mov rdi, 1
        mov rsi, hello_world
        mov rdx, hello_world_len
        syscall
        mov rax, 60
        mov rdi, 0
        syscall

Compiled with:

nasm -w+all -f elf64 -o 'hello_world.o' 'hello_world.asm'
ld -o 'hello_world.out' 'hello_world.o'

TODO: use a minimal linker script with -T to be more precise and minimal.

Versions:

NASM 2.10.09
Binutils version 2.24 (contains ld)
Ubuntu 14.04

We don't use a C program as that would complicate the analysis, that will be level 2 :-)

ELF Hello World Tutorial / Index 0 section Updated 2025-07-16

Contained in bytes 0x40 to 0x7F.

The first section is always magic: www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html says:

If the number of sections is greater than or equal to SHN_LORESERVE (0xff00), e_shnum has the value SHN_UNDEF (0) and the actual number of section header table entries is contained in the sh_size field of the section header at index 0 (otherwise, the sh_size member of the initial entry contains 0).

There are also other magic sections detailed in Figure 4-7: Special Section Indexes.

ELF Hello World Tutorial / Minimal ELF file Updated 2025-07-16

It is non-trivial to determine what is the smallest legal ELF file, or the smaller one that will do something trivial in Linux.

Some impressive attempts:

In this example we will consider a saner hello world example that will better capture real life cases.

ELF Hello World Tutorial / .rel.text Updated 2025-07-16

Besides sh_type == SHT_RELA, there also exists SHT_REL, which would have section name .text.rel (not present in this object file).

Those represent the same struct, but without the addend, e.g.:

typedef struct {
    Elf64_Addr  r_offset;
    Elf64_Xword r_info;
} Elf64_Rela;

The ELF standard says that in many cases the both can be used, and it is just a matter of convenience.