Properties of DES S-Box

[drew99]

Someone is able to explain to me the construction and operation of the DES S-Box, which from n input bits input, produces an output of m bits, with m <n?

I found some material, but I can't understand it:
http://it.wikipedia.org/wiki/S-Box
http://en.wikipedia.org/wiki/DES_supplementary_material

Thanks in advance for your answers.

[meganewbie]

cross posted

http://cboard.cprogramming.com/c-programming/151827-des-s-box.html

Also here: http://forums.devshed.com/c-programming-42/reproduce-an-s-box-933181.html

[drew99]

If it isn't cross-posting, can someone remove "meganewbie" messages?
Then, can somebody explain me this part of the algorithm?
Thanks to all.