Jazz fusion Updated 2025-07-16
Ciro's 2020 perfect Friday evening: jazz fusion + study quantum field theory on an Amazon Kindle. Ahhhhhh.
It is non-trivial to determine what is the smallest legal ELF file, or the smaller one that will do something trivial in Linux.
In this example we will consider a saner hello world example that will better capture real life cases.
Joan Feynman Updated 2025-07-16
Video 1.
My brother, Richard: How he came to be so smart interview with Joan Feynman by Web of Stories (2019)
Source. Ah, shame to see Joan so old. Some good stories. The tiles game thing was not mentioned in Genius: Richard Feynman and Modern Physics by James Gleick (1994) I think.
ELF Hello World Tutorial / .symtab Updated 2025-07-16
Section type: sh_type == SHT_SYMTAB.
Common name: "symbol table".
First the we note that:
  • sh_link = 5
  • sh_info = 6
For SHT_SYMTAB sections, those numbers mean that:
  • strings that give symbol names are in section 5, .strtab
  • the relocation data is in section 6, .rela.text
A good high level tool to disassemble that section is:
nm hello_world.o
which gives:
0000000000000000 T _start
0000000000000000 d hello_world
000000000000000d a hello_world_len
This is however a high level view that omits some types of symbols and in which the symbol types . A more detailed disassembly can be obtained with:
readelf -s hello_world.o
which gives:
Symbol table '.symtab' contains 7 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS hello_world.asm
     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1
     3: 0000000000000000     0 SECTION LOCAL  DEFAULT    2
     4: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT    1 hello_world
     5: 000000000000000d     0 NOTYPE  LOCAL  DEFAULT  ABS hello_world_len
     6: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT    2 _start
The binary format of the table is documented at www.sco.com/developers/gabi/2003-12-17/ch4.symtab.html
The data is:
readelf -x .symtab hello_world.o
which gives:
Hex dump of section '.symtab':
  0x00000000 00000000 00000000 00000000 00000000 ................
  0x00000010 00000000 00000000 01000000 0400f1ff ................
  0x00000020 00000000 00000000 00000000 00000000 ................
  0x00000030 00000000 03000100 00000000 00000000 ................
  0x00000040 00000000 00000000 00000000 03000200 ................
  0x00000050 00000000 00000000 00000000 00000000 ................
  0x00000060 11000000 00000100 00000000 00000000 ................
  0x00000070 00000000 00000000 1d000000 0000f1ff ................
  0x00000080 0d000000 00000000 00000000 00000000 ................
  0x00000090 2d000000 10000200 00000000 00000000 -...............
  0x000000a0 00000000 00000000                   ........
The entries are of type:
typedef struct {
    Elf64_Word  st_name;
    unsigned char   st_info;
    unsigned char   st_other;
    Elf64_Half  st_shndx;
    Elf64_Addr  st_value;
    Elf64_Xword st_size;
} Elf64_Sym;
Like in the section table, the first entry is magical and set to a fixed meaningless values.
Elon Musk Updated 2025-07-16
Musk is a truly ambivalent personality. Some points are very good. Some are very bad.
Respect on the technical side by Ciro Santilli.
But the way he treated his first wife Justine Musk, is very very weird, incomprehensible: www.marieclaire.com/sex-love/a5380/millionaire-starter-wife/
Positive Cirocoins for possibly going to reverse Twitter's unfair Trump ban if his Twitter acquisition goes through:
Negative Cirocoins for according to Wikipedia:
Within the merged company [Thiel's Confinity + Elon's X.com], Musk returned as CEO. Musk's preference for Microsoft software over Unix created a rift in the company and caused Thiel to resign.
Video 1.
The REAL Reason Why Tesla Made All Patents Open-Source by The not so boring Man (2021)
Source. Supercut from various interviews/presentations in which Elon saying that Tesla has open source patents and pro open source stuff. Can we trust it? Maybe.
Engine Updated 2025-07-16
Enthalpy Updated 2025-07-16
Adds up chemical energy and kinetic energy.
Wikipedia mentions however that the kinetic energy is often negligible, even for gases.
The sum is of interest when thinking about reactions because chemical reactions can change the number of molecules involved, and therefore the pressure.
To predict if a reaction is spontaneous or not, negative enthalpy is not enough, we must also consider entropy via Gibbs free energy.
Epic Rap Battles of History Updated 2025-07-16
Most of the videos are crap, but the following ones almost killed Ciro Santilli of laughter:
Video 1.
Rasputin vs Stalin by Epic Rap Battles of History (2013)
Source. See also: cirosantilli.com/china-dictatorship/stalin.
Monty Python has a few precursors to the "random famous people mixed together compting" format, although not in the rap fight format:
Video 3.
Philosophers' Football Match by Monty Python (1972)
Source. If you can understand the jokes, your philosophy level is pretty good. Like more than zero. Wiki page: en.wikipedia.org/wiki/The_Philosophers%27_Football_Match. Ciro loves how that page currently uses a standard footbal match template to describe the match!
Ethernet cable Updated 2025-07-16
When non-specialists say "Ethernet cable", they usually mean twisted pair for Ethernet over twisted pair.
But of course, this term is much more generic to a more specialized person, since notably fiber optics are also extensively used in Ethernet over fiber.
A good project to see UARTs at work in all their beauty is to connect two Raspberry Pis via UART, and then:
Part of the beauty of this is that you can just connect both boards directly manually with a few wire-to-wire connections with simple jump wire. Its simplicity is just quite refreshing. Sure, you could do something like that for any physical layer link presumably...
Remember that you can only have one GNU screen connected at a time or else they will mess each other up: unix.stackexchange.com/questions/93892/why-is-screen-is-terminating-without-root/367549#367549
On Ubuntu 22.04 you can screen without sudo by adding yourself to the dialout group with:
sudo usermod -a -G dialout $USER
Existence of the matrix logarithm Updated 2025-07-16
en.wikipedia.org/wiki/Logarithm_of_a_matrix#Existence mentions it always exists for all invertible complex matrices. But the real condition is more complicated. Notable counter example: -1 cannot be reached by any real .
The Lie algebra exponential covering problem can be seen as a generalized version of this problem, because
Existential risk of AGI Updated 2025-07-16
www.cam.ac.uk/research/news/the-best-or-worst-thing-to-happen-to-humanity-stephen-hawking-launches-centre-for-the-future-of
The rise of powerful AI will either be the best or the worst thing ever to happen to humanity. We do not yet know which.
University Updated 2025-09-09
One major issue is that teachers don't have the right incentive to, nor are selected to, teach well. Thus the existence of Rate My Professors! But we can do better...
Which is why Ciro Santilli wants to destroy its current format with OurBigBook.com. He believes that we can find a more efficient organization to achieve both the social and research functions of university, by first doing as much as possible online
Fabless manufacturing Updated 2025-07-16
In the past, most computer designers would have their own fabs.
But once designs started getting very complicated, it started to make sense to separate concerns between designers and fabs.
What this means is that design companies would primarily write register transfer level, then use electronic design automation tools to get a final manufacturable chip, and then send that to the fab.
It is in this point of time that TSMC came along, and benefied and helped establish this trend.
The term "Fabless" could in theory refer to other areas of industry besides the semiconductor industry, but it is mostly used in that context.
FFmpeg Updated 2025-07-16
FFmpeg is the assembler of audio and video.
As a result, Ciro Santilli who likes "lower level stuff", has had many many hours if image manipulation fun with this software, see e.g.:
As older Ciro grows, the more he notices that FFmpeg can do basically any lower level audio video task. It is just an amazing piece of software, the immediate go-to for any low level operation.
FFmpeg was created by Fabrice Bellard, which Ciro deeply respects.
Resize a video: superuser.com/questions/624563/how-to-resize-a-video-to-make-it-smaller-with-ffmpeg:
ffmpeg -i input.avi -filter:v scale=720:-1 -c:a copy output.mkv
Unlike every other convention under the sun, the height in scale is the first number.

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