Wait, is it multiplication like your title says, or is it addition? How many polynomial's will their be?
If there are only 2 polynomial's and you want to add: Load monomial's into list 1 (store coefficient and vairable) for polynomial 1. Do the same in another list for polynomial 2. Scan through list 1, and check for dublicate variables. If any vaiable's are found, add them onto matching node's. Do the same for list 2. Scan through list 1 and check for matching variable's in list 2. If they are found, add them into matching node's in list 2. If they are not found, add them to the end of list 2 (in a new node).
download Turbo C and install it on my 21st Century machine, just so I can ... compile some broken-down code that won't work anyhow?
now, seriously. you need to wheel that trash on out of here. Take it home and fix it up. bring us back a C program that can ACTUALLY COMPILE, not some bastardized C/C++ hybrid, and none of these deprecated libraries from 1989.
Then and only then will i bother to compile it and verify it is indeed still broken, anyhow. and then you can go donate $20 to some charity.