C1D00000 = 1100 0001 1101 0000……0000
In IEEE representation for single precision floating point numbers, first bit is for sign, next 8 bits for exponent and last 23 bits for mantissa which excludes the implicit "1" before ".", unless the number is not normalized (happens only when exponent is 0 and mantissa is non zero).
First bit = sign bit = 1, so number is negative
exponent $= 131 - 127 = 4$ (127 is the bias in IEEE representation).
significant $= 1. 101\underbrace{000\dots 0}_{\text{20 0's}} \\=(1)2^0 + (1)2^{-1} + (0)2^{-2 }+ (1)2^{-3} \\= 1 + 1/2 + 0 + 1/8 = 13/8$
hence we finally get decimal value
$= \text{sign} \times 2^{\text{exponent}} \times \text{significant} = -26$.
