Useful URLS

on logic gates

http://whatis.techtarget.com/definition/0,,sid9_gci213512,00.html

http://www.kpsec.freeuk.com/gates.htm#symbols

http://en.wikipedia.org/wiki/Logic_gate

simulators for logic gates

http://web.mit.edu/ara/www/ds.html

http://www.softronix.com/logic.html

on hashing with definitions and an animation:

http://ciips.ee.uwa.edu.au/~morris/Year2/PLDS210/hash_tables.html

on hash functions:

http://ciips.ee.uwa.edu.au/~morris/Year2/PLDS210/hash_func.html

from wikipedia

http://en.wikipedia.org/wiki/Hash_function