Fibonacci numbers
This program prints out the first n numbers in the Fibonacci sequence. In case you are unfamiliar with the Fibonacci sequence, the first two numbers are both 1, and from then on each following number is equal to the sum of the previous two.
To demonstrate:
| Computation | Fibonacci number |
|---|---|
| 1 | 1 |
| 1 | 1 |
| 1 + 1 | 2 |
| 1 + 2 | 3 |
| 2 + 3 | 5 |
| 3 + 5 | 8 |
| 5 + 8 | 13 |
| 8 + 13 | 21 |
| 13 + 21 | 34 |
Programming Issues
The computations are done using a simple for loop,
using two variables (f1 and f2) to hold
each pair, and a temporary variable used when updating them. The
Fibonacci sequence can be computed recursively, but this is a much
less efficient way in this case.
The number of numbers to calculate is passed via the command line,
and extracted by ParseCmdLine(). The number must be
greater than 2 (because the first two numbers are always output)
and less than 48 (because unsigned long is not guaranteed
to hold numbers larger than 4,294,967,295).
Usage
Pass the desired number as the sole command line argument. A sample session is shown below:
[paul@hermes fibo]$ ./fibo 47
First 47 numbers in the Fibonacci sequence:
1 1 2 3 5
8 13 21 34 55
89 144 233 377 610
987 1597 2584 4181 6765
10946 17711 28657 46368 75025
121393 196418 317811 514229 832040
1346269 2178309 3524578 5702887 9227465
14930352 24157817 39088169 63245986 102334155
165580141 267914296 433494437 701408733 1134903170
1836311903 2971215073