For those outside of USA:
Telephone
area codes are 3 digits. The older area codes have a 0 or 1 in the middle digit due to requirements of (now obsolete) "crossbar" switching systems. So if you see a x0x or x1x number, you can safely figure it's an area code and an older one.
My area code is a newer one: 386, which spells "FUN" on the keypad.
Postal
zip codes are 5+4, meaning 5 is the common length with (sometimes) 4 additional digits. The full 9 digit codes are usually used by business and other mass mailers. So you'll usually see just 5 digits.
Most zip codes cover a much
smaller geographical area than area codes.
