A black screen on your computer can mean several things. A black screen is most commonly a screen saver, but there are other possibilities. My computer switches to a black screen after about 5 to 15 minutes of use. Then I have to turn it off to get another 5 to 15 minutes of use.
Time and frequency domain for the same signal. A fast Fourier transform (FFT) algorithm computes the discrete Fourier transform (DFT) of a sequence, or its inverse. Fourier analysis converts a signal from its original domain (often time or space) to a representation in the frequency domain and vice versa.ime and frequency domain for the same signal. A fast Fourier transform (FFT) algorithm computes the discrete Fourier transform (DFT) of a sequence, or its inverse. Fourier analysis converts a signal from its original domain (often time or space) to a representation in the frequency domain and vice versa.
Ryan's answer sums it up. I will however expand a bit. The FFT is a fast implementation of the DFT. When we apply a naive DFT to a signal of length [math]N[/math] we need to multiply an [math]N\times N[/math] matrix by a [math]N \times 1[/math] vector, which requires roughyly [math]O(N^2)[/math] operations.