Someone who knew me well enough to use my own words and personal code.

The 13-digit code took off and is used in most other countries.

I'm sure these guys will be using code or such to report their progress home.

But he would reach them by using various codes from the past.

I gave up on trying to use other people's code after several bad experiences.

Each code would be used to send only one message.

However, between 1966 and 1968, some old codes were used.

For example, 1+3 and 6-2 both achieve the same result while using different code.

Secret codes are also used on almost everything you buy.

For example, 3+1 and 6-2 both achieve the same result, yet use completely different code.