up according to the formula. The only concern is that all computations for F(1), F(2),... up to F(N) are being made, even though they are not themselves wanted. Having settled on a basic method does not determine fully the actual processing, as we show below by giving several designs.

SOLUTION I

Figure FIB-i shows a straightforward design for a Fibonacci number generator. F(0) and F(1) are generated at the beginning of the process and the normal exit is taken for N = 0,1; for N greater than I but small enough not to cause overflow, the loop is performed N-1 times yielding F(N), N is decremented by 1 on each pass through the loop, and the normal exit is taken when N = 0. For those N such that F(N) >2^16, overflow will occur and the overflow exit is taken.