By Charles Petzold December 12, 2021 ⋅ 2 min read ⋅ Books
NOTE: This is an incomplete set of notes.
Preface
Metaphors and similes are wonderful literary devices but they do nothing but obscure the beauty of technology.
The distinction between memory and storage is an artificial one and exists solely because we don’t have a single storage medium that’s both fast, vast, and nonvolatile.
What we know today as the “von Neumann architecture”, the dominant computer architecture, is a direct result of this technical deficiency.
Code: a system of signals used to represent letters or numbers in transmitting messages. A system of symbols given certain arbitrary meanings used for transmitting messages requiring secrecy or brevity.
Chapter 1: Best Friends
Can flashlights be made to speak?
Review of Morse code where every letter of the alphabet matches a short series of dots and dashes.
Code: a system for transferring information among people and machines.
In other words, a code lets you communicate, sometimes in secret, but most times not.
There seems to be no reason why cats aren’t called “dogs” and dogs aren’t called “cats.
You could say English vocabulary is a type of code.
A code is useful if it serves a purpose that no other code can.
Computers can’t deal with human codes directly because computers can’t duplicate the ways in which human beings use their eyes, ears, mouths, and fingers.
Chapter 2: Codes and Combinations
The invention of Morse code goes hand-in-hand with the invention of the telegraph.
Most people find it easier to send Morse code than to receive it because most Morse code tables go from alphabetical letter → Morse code dots and dashes and not the reverse.
But it isn’t obvious how we could construct such a table.
numberofcodes=2numberofsymbols
To make the process of decoding Morse code even easier, we could make a treelike table.
Undefined: a code that doesn’t stand for anything.
Chapter 3: Braille and Binary Codes
Review of the invention of Braille inspired by Barbier’s system.
Precedence/shift codes: codes that alter the meaning of the codes that follow them.
E.g. Number indicator and capital indicator.
Chapter 4: Anatomy of a Flashlight
Review of electrons, atoms, and molecules.
Review of electricity, conductors, and insulators.
Chapter 5: Seeing Around Corners
Review of the ground/earth electrical component.
Chapter 6: Telegraphs and Relays
I’m dropping this book at chapter 6 because I learned most of this book in school already. This would be a great book for reviewing the material or for beginners, but not for educated electrical and software engineers.