real and imaginary complex I(FFT)

How to separate the real number from the imaginary number in the complex number? with I(FFT).

like

a+bi

a2+bi2

.

.

.

to a

a2

...

bi

bi2

.

.

Answer 1

[madhan ravi]

real()
imag()

[abdullah qasim]

but how saperate the complex number