What is Oracle Pro*C ?

Here is a chapter from a book on Oracle 10 that describes Pro*C as Embedded SQL

http://tinman.cs.gsu.edu/~raj/books/oracle10-primer.html

The wikipedia page on Pro*C

http://en.wikipedia.org/wiki/Pro*C
 
Pro-C Tutorial with programming examples
 
http://programmingexamples.wikidot.com/pro-c-tutorial

There seems to be both a SAS PROC and an Oracle Pro*C that do the same thing.
Both are basically a means of embedding sql code in a c or c++ program.


Questions

How is embedded SQL different from just a stored procedure?
Why would you embed SQL scripts in a C program?
Is this useful for systems integration issues?
How does this relate to middleware or messaging?