The exponent in IEEE32 has a fixed offset of 127 to always have positive values:
exp (500.0,IEEE32) = 8+127 == 87 (hex) == 10000111 (bin)
The fields must be put together as shown the following listing:
500.0 (dec) = 0 (sign) 10000111 (exponent) 11110100000000000000000 (mantissa) (IEEE32 as bin) 0100 0011 1111 1010 0000 0000 0000 0000 (IEEE32 as bin) 43 fa 00 00 (IEEE32 as hex)
The IEEE32 representation of decimal -500 is shown in the following listing.
-500.0 (dec) = 1 (sign) 10000111 (exponent) 11111010000000000000000 (mantissa) (IEEE32 as bin) 1100 0011 1111 1010 0000 0000 0000 0000 (IEEE32 as bin) C3 fa 00 00 (IEEE32 as hex)