how to perform addition substraction on a 200 digit number in 'C'????? how to read that big number?? i have to do it in float. someone spoke of 'big float', wat is that??

You can't do it with the built-in types; you will have to implement your own. One way is to represent the numbers with strings, e.g. Code: char *pi="3.1415926535897932384626450288"; which will retain its accuracy as long as you want it to (i.e. there is no conversion to binary). Adding/subtracting numbers will be just an implementation of how you did this back in school. Remember doing sums like this one? 12345 2008+ ===== 5+8 is 13, carry 1 and write 3. 4+0+1 is 5. And so on.