This field is a good example for discussing a problem that crops up in programming all the time, it is particularly significant if a Database is involved

What is a Zip Code

(or more generally what could the data look like)

How do I get the Zip Code

90046

90046-0021

The Zip above could be expressed as an INT but is it a complete Zip?

This Zip is actually 90025 if expressed as an INT (or an error depending on the interpreter)

I might even question should it be a VARCHAR?

Everything input by a human starts out as a String Variable

Humans do not follow instructions and will put weird data into you fields

Why Is Zip a CHAR And Not a INT ?