For anyone here who's never pondered it ("today's lucky 10,000"?), there's a lot of intentional structure in the organization of ASCII that comes through readily in binary or hex.

https://altcodeunicode.com/ascii-american-standard-code-for-...

The first nibble (hex digit) shows your position within the chart, approximately like 2 = punctuation, 3 = digits, 4 = uppercase letters, 6 = lowercase letters. (Yes, there's more structure than that considering it in binary.)

For digits (first nibble 3), the value of the digit is equal to the value of the second nibble.

For punctuation (first nibble 2), the punctuation is the character you'd get on a traditional U.S. keyboard layout pressing shift and the digit of the second nibble.

For uppercase letters (first nibble 4, then overflowing into first nibble 5), the second nibble is the ordinal position of the letter within the alphabet. So 41 = A (letter #1), 42 = B (letter #2), 43 = C (letter #3).

Lowercase letters do the same thing starting at 6, so 61 = a (letter #1), 62 = b (letter #2), 63 = c (letter #3), etc.

The tricky ones are the overflow/wraparound into first nibble 5 (the letters from letter #16, P) and into first nibble 7 (from letter #16, p). There you have to actually add 16 to the letter position before combining it with the second nibble, or think of it as like "letter #0x10, letter #0x11, letter #0x12..." which may be less intuitive for some people).

Again, there's even more structure and pattern than that in ASCII, and it's all fully intentional, largely to facilitate meaningful bit manipulations. E.g. converting uppercase to lowercase is just a matter of adding 32, or logical OR with 0x00100000. Converting lowercase to uppercase is just a matter of subtracting 32, or logical AND with 0x11011111.

For reading hex dumps of ASCII, it's also helpful to know that the very first printable character (0x20) is, ironically, blank -- it's the space character.

I should just have put the printable character chart right here in the post for people to compare:

     0 1 2 3 4 5 6 7 8 9 A B C D E F
  ..
  2    ! " # $ % & ' ( ) * + , - . / 
  3  0 1 2 3 4 5 6 7 8 9 : ; < = > ? 
  4  @ A B C D E F G H I J K L M N O 
  5  P Q R S T U V W X Y Z [ \ ] ^ _ 
  6  ` a b c d e f g h i j k l m n o 
  7  p q r s t u v w x y z { | } ~

> the character you'd get on a traditional U.S. keyboard layout

I use a different layout so I'd never realised there was method to the madness! I get the following

$ echo -n ' !@#$%^&*(' | xxd -p 2021402324255e262a28