What is difference between float-extended-exponent and float in java

Question

The section 2.8.2. Floating-Point Modes of the Java Virtual Machine Specification describes about float-extended-exponent and float value sets.

1. What does it mean?
2. In what way does it affect the floating point representation in the program ?
3. What are floating-point modes?
4. Which representation is supported by most implementations ?

Answer 1

See section 2.3.2, and Table 2.1, of the page you linked. The different "value sets" can represent different ranges of numbers.

The finite nonzero values of any floating-point value set can all be expressed in the form s ⋅ m ⋅ 2^{e − N + 1}, where s is +1 or −1, m is a positive integer less than 2N, and e is an integer between Emin = −(2^{K−1}−2) and Emax = 2^{K−1}−1, inclusive, and where N and K are parameters that depend on the value set.

The "extended-exponent" value sets have larger K values than the non-extended-exponent. That means they can handle numbers that are larger in magnitude than the non-extended-exponent value sets.