How can I use Keil to compute exponential function? is use #include <stdlib.h>? thank you sir.
I need to calc complex number on 8051 because of I have to calc FFT. Actually, you don't. Using the exponential notation in frequency analysis is merely a convenient way to pack a sine and a cosine function into a single expression. The only complex operations necessary are addition/subtraction and multiplication, which are trivial to implement. If you're using anything like calls to exponential or trigonometric library functions (instead of just using a lookup table), you're essentially doing the exact opposite of a Fast Fourier Transform, because the resulting code will run very slowly.
http://en.wikipedia.org/wiki/Cooley-Tukey_FFT_algorithm http://www.fftw.org/