ASCII Codes

1. ASCII 32 = Space
2. ASCII 48 = 0
3. ASCII 65 = A
4. Lowercase codes are uppercase codes + 32

Knowing ASCII 48 is 0 means you know the ASCII codes for 0 - 9 (they're consecutive).

Knowing ASCII 65 is A means you know the ASCII codes for A - Z (they're consecutive). Adding 32 to any of these ASCII codes gives you the ASCII codes for a - z.

This gives you 63 out of 95 printable standard ASCII characters. Pretty good for only remembering four facts.