Fibonacci Sequence in C generating negatives?

Question

I\'m new to programming and need help in C. I am writing a program to generate a Fibonacci sequence for values with up to 1000 digits.

Here is my code:

Answer 1

The comment I posted above has the simple answer, but here's a more complete version: C often represents integers with a sequence of 32 bits, and the range of values they can take on are from -2,147,483,648 to 2,147,483,647.

Notice what the 47th Fibonacci number is? 2,971,215,073

After they overflow, they wrap around to the smallest integer possible; see 2's complement notation for more information!

For a solution, I might suggest a BigInteger structure. But Fibonacci numbers get huge really fast, so I'm not sure you'd really want to calculate that many.