Yes, family income is absolutely an example of a continuous variable.
but zip code ,i think, is not a continuous variable
It is not continuous.
There are approximately 43000 zip codes. Number of ZIP codes periodically changes. For example, around 200 zip codes were added in the U.S. in 2006-2007.
Zip Codes are only used in the United States. There are no international zip codes.
Yes they can be. Zip codes are used to identify market areas so they can market more, such as sending mail, fliers, or coupons to the zip codes or areas that shop more at their stores.
Numbers are used in zip codes.
There are many (maybe hundreds) of zip codes for the state of Califorina. See related links and look up the zip code for a specific city (even then you may get a dozen or so zip codes if you do not know the address).
27 zip codes
OK. States don't have Zip Codes. Cities have Zip Codes. You can get the complete list of ZIP codes in California under different Cities from here: http://www.zip4all.com/california/ca/ .
Yes. Japan has zip codes just like we do but their zip codes are seven numbers long as opposed to us, where we just have six digit zip codes. Below are some examples
The zip codes are: 95380, 95381, 95382.
For Denmark zip codes see the related link.
33 zip codes