[Help] What is an hash code?

Hello,
what can i do with a hash code?
im asking because of this:
http://www.mpgh.net/forum/33-visual-...ns-vb-net.html
Please tell me what is it/

In cryptography, MD5 (Message-Digest algorithm 5) is a widely used cryptographic hash function with a 128-bit hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of files. However, it has been shown that MD5 is not collision resistant; as such, MD5 is not suitable for applications like SSL certificates or digital signatures that rely on this property. An MD5 hash is typically expressed as a 32-digit hexadecimal number.



EVERY file has a different md5 hash even if you just change one char in a textfile, the md5 hash will be different.

This is useful for updaters for instance.

It is alphabetic-numeric.

That explains a lot alcohol.

From my understanding the Hash code is use for compare.
GetHashCode() is used to compare. This one Example is help to how to use hash code .

person p = new person("Mark", "Taylor");
person pp = new person("Mark", "Taylor");
int i = p.GetHashCode();
int ii = p.GetHashCode();

The hash of a file is its representation based on a mathematical algo. The hash of that file is unique to that file. And as such can be used to determine if 2 files are the same.