I have an discrete maths exhibition, and i wanted to illustrate the influence of discrete maths in computer science.

so i need some softwares to illustrate. A few examples like set theory for computer networking. graph theory and big O for analysis of algoritms.

please can some of you suggest some software. thanks.
remember it must show influence of discrete maths

I am not sure about this, but does PERT/CPM fall under discrete maths ?
If yes these are used in project scheduling and management and hence in the s/w made for such systems.

As far as demonstrating big O - you're not going to be able to easily write programs which analyze running time of other programs. The easiest demonstration would be to look at some execution data for several runs through various finite data sets over some different algorithms that belong to different runtime classes. Perhaps a good example would be sorting using bubble, insertion, quicksort, heapsort and radix-sorts. Standard compsci - easily accessible and easily understood.

As to 'set theory' maybe you should look at the following::
1) simple ball/urn w/wo replacements
2) poker hand probabilities ... maybe even use 2 decks of cards
3) polyominoes

As far as graph theory algorithms go - you can do a lot in very little time if you have a CAS/Math program like maple, mathematica or sage handy.
If you want to sketch some graphs out by hand or by feeding it datasets from your application code then look at ::
tulip (http://www.tulip-software.org/)
graphviz ( http://www.graphviz.org/ )
uDraw ( http://www.informatik.uni-bremen.de/...DrawGraph.html )

C++ya,
xkey