ASCII: The Foundation (1963)

ASCII = American Standard Code for Information Interchange

Key Facts:

• 7 bits: 2⁷ = 128 possible characters (0-127)
• Coverage: English alphabet, numbers, punctuation, control codes
• Designed for: English language, teletype machines, early computers
• File size: 1 byte per character (8 bits, with 1 bit spare)

ASCII Character Ranges:

  0-31:    Control characters (e.g., newline, tab, delete)
  32:      Space
  33-47:   Punctuation (! " # $ % & ' ( ) * + , - . /)
  48-57:   Digits (0-9)
  58-64:   More punctuation (: ; < = > ? @)
  65-90:   Uppercase letters (A-Z)
  91-96:   Brackets and symbols ([ \ ] ^ _ `)
  97-122:  Lowercase letters (a-z)
  123-127: More symbols ({ | } ~ DEL)
  

Common ASCII Codes (Memorize These!):

Character	ASCII Code	Binary	Hex
0 (digit)	48	00110000	30
9 (digit)	57	00111001	39
A (uppercase)	65	01000001	41
Z (uppercase)	90	01011010	5A
a (lowercase)	97	01100001	61
z (lowercase)	122	01111010	7A
Space	32	00100000	20

Clever ASCII Patterns:

• 'A' = 65, 'B' = 66, 'C' = 67... Sequential codes make alphabetical sorting easy
• Uppercase → Lowercase: Add 32 ('A' (65) + 32 = 'a' (97))
• Digit characters: '0'=48, '1'=49... To get numeric value, subtract 48