Understanding 32 bits image mode

Hi

i'm developping a plugin in which higher image quality means higher sound quality.

though when i'm in mode 32 bits, colors don't behave the same way as in 8 bits or 16 bits.

for example, in 8 bits i have

R = 128;

g = 255;

b = 128;

it will not be the same color as in 32 bits:

R = 0.5;

G = 1;

B = 0.5;

(in 32 bits, is it much brighter)

how come ?

how do i do to use 32 bits mode with the same color scheme as in 8 or 16 bits?

thanks

Jeff