hello frds,
i am provided with assignments for evaluation of stack (i.e conversion of prefis ,postfix, infix into each other) i tried for a long time and had to go for searching on net i need it urgently .plzzzzz if any1 knows it let me know

What did you try and where did you search? I get plenty of hits on google for this sort of thing, and several books go over it during their explanation of stacks.

well i just need a explaination abt these programms .can anybody help me???????
i need it urgently and really didnt found it on net

>really didnt found it on net
BS. Just about every google hit on the first page of a search for "infix prefix postfix conversion" looks promising. Either you didn't search as hard as you're suggesting, or you were too lazy to try searching and thought we would fall for a lie.