How do I initialize a variable bigger than a double?

I want to make a maths program for college but I need some of my variables to havea greater accuracy than a double can offer. They have to be numerical and capable of understanding decimals. I'm sure this can be done but I dont know how?

Thanks

Try using a long double.

If that still isn't big enough you can create your own class based on a list/array of int/char overloading all the math operators in addition to the routine variety of constructors, assignment operators, etc.