Answer from cs61c-ck (Allen Lee 16583554) for Question 2
Subnormals, or denormalized numbers, are normals with the same exponent as zero but have a nonzero significand.  Subnormals are simply floating-point numbers that are precise than normalized numbers because they treat the leading zeros in the significand as actual zeros in the scientific notation, for example 0.00....01_two x 2^-126.