What is Hashing or Hashing Function?

hi all,
lately, i heard ppl talking about this 'hashing function', 'hashing check' what in the world does that totally means? i got really no idea in that. pls someone, give me a clear explanation on this. thks

longwar

Wikipedia explains Hash function pretty well.

Moved to General Developer

We use hash logic in bank transmissions...

Let's say we want to put the figure 123456 into a file for transmitting. They want to make sure the file arrives without any transmission errors and that the 123456 came across cleanly.

You can add the digits 1+2+3+4+5+6 = 21 and then put the "last" digit of the "hash" 21 onto the string - making 1234561 be the transmitted value.

Now when reviewing the figure - you take the first 6 digits and make sure the "hash" returns a value ending in "1".

There are many different ways of doing this - just a simple example...