binary and floating point representation suppose that we have following  binary digits
$00011001.110 $,we can do following thing
$00011001.110=1\cdot2^4+1\cdot2^3+1\cdot2^0+1\cdot2^{-1}+1\cdot2^{-2}=25.75$ 
then  what does means?
We then “float” the binary point:
$00011001.110 \Rightarrow 1.1001110 \cdot 2^4 $
mantissa = 1.1001110, exponent = 4
i did not understand this part,generally for sign  we have  $1$ bit,for exponent we have $8$ bit and for mantissa we need   $23$ bit,so i can't understand last part,from floating to binary point,please help me

I'm not sure I really get your question, but are you confused about what "mantissa" really means - it should be a 2-complement integer, but in normalized representation it has a leading "1."? In the standard, the leading "1." is implied: the mantissa bits represent, in your case, only 100111. If this isn't your point of confusion, kindly elaborate more. 
