Was the fast Fourier algorithm of Cooley-Turkey patented at that time?

Because patents need to solve technical problems and produce technical effects, pure algorithms can't apply for patents. Only by applying this method to solve practical problems can we apply for patents. For example, a matrix algorithm that can improve the speed of computer operation, or some path algorithms in topology, can be patented if applied to the network to find the optimal transmission path.

Therefore, if the fast Fourier algorithm is not combined with practical application, it will not be patented. If you really want to apply, you can consider the following, because fast Fourier transform is widely used in signal processing now, so for example, circuits, processing systems and even optical application devices that realize fast Fourier transform can apply for patents.

Of course, the protection objects of patent laws in different countries are different, but they are basically universal, and it is normal for any country in the world not to obtain patents for algorithms.