# float/double extended exponent value sets-Can someone answer this?

sanjana narayanan

Ranch Hand

Posts: 142

posted 12 years ago

Hi,

I have a problem understanding the float exponent extended value and double extended exponded value. Can someone explain this to me?

This following para is taken from JLS 4.2.3 UNDER THE Topic Types,Values and variables. I do not understand even a single part of it.

The finite nonzero values of any floating-point value set can all be expressed in the form , where s is +1 or -1, m is a positive integer less than , and e is an integer between and , inclusive, and where N and K are parameters that depend on the value set. Some values can be represented in this form in more than one way; for example, supposing that a value v in a value set might be represented in this form using certain values for s, m, and e, then if it happened that m were even and e were less than , one could halve m and increase e by 1 to produce a second representation for the same value v. A representation in this form is called normalized if ; otherwise the representation is said to be denormalized. If a value in a value set cannot be represented in such a way that , then the value is said to be a denormalized value, because it has no normalized representation.

-Sanjana

I have a problem understanding the float exponent extended value and double extended exponded value. Can someone explain this to me?

This following para is taken from JLS 4.2.3 UNDER THE Topic Types,Values and variables. I do not understand even a single part of it.

The finite nonzero values of any floating-point value set can all be expressed in the form , where s is +1 or -1, m is a positive integer less than , and e is an integer between and , inclusive, and where N and K are parameters that depend on the value set. Some values can be represented in this form in more than one way; for example, supposing that a value v in a value set might be represented in this form using certain values for s, m, and e, then if it happened that m were even and e were less than , one could halve m and increase e by 1 to produce a second representation for the same value v. A representation in this form is called normalized if ; otherwise the representation is said to be denormalized. If a value in a value set cannot be represented in such a way that , then the value is said to be a denormalized value, because it has no normalized representation.

-Sanjana

Gian Franco

blacksmith

Ranch Hand

Ranch Hand

Posts: 979

posted 12 years ago

Hi Sanjana,

The following URL might help:

http://www.javaworld.com/javaworld/jw-10-1996/jw-10-hood_p.html

Gian Franco

The following URL might help:

http://www.javaworld.com/javaworld/jw-10-1996/jw-10-hood_p.html

Gian Franco

"Eppur si muove!"

Rolf W. Rasmussen

Author

Greenhorn

Greenhorn

Posts: 5

posted 12 years ago

Ahh, you're looking at shorthand description of the IEEE Floating Point

Standard (IEEE 754) that the Java Language specification uses to

describe the behavior of the float and double types.

The formulas in the text you pasted got lost, making the text even harder

to interpret than it already was.

First off, let me assure you that you don't have to understand these

formulas to pass the certification exam.

Things relevant for the exam are:

The upper and lower bound of the types. Knowing which operations will result in NaN, and +/- INF. Knowing that loss of precision can occur.

For a bit more readable presentation of the IEEE Floating Point

Standard (IEEE 754) representation, you can read:

http://en.wikipedia.org/wiki/IEEE_Floating_Point_Standard

http://www.d6.com/users/checker/pdfs/gdmfp.pdf

Just keep in mind that the bit patterns presented does not necessarily

directly correspond to the in-memory patterns used by the Java VM.

The only thing that is guaranteed is that the externally visible effect

of the mathematical operations are identical to the ones specified

by IEEE 754.

Standard (IEEE 754) that the Java Language specification uses to

describe the behavior of the float and double types.

The formulas in the text you pasted got lost, making the text even harder

to interpret than it already was.

First off, let me assure you that you don't have to understand these

formulas to pass the certification exam.

Things relevant for the exam are:

For a bit more readable presentation of the IEEE Floating Point

Standard (IEEE 754) representation, you can read:

http://en.wikipedia.org/wiki/IEEE_Floating_Point_Standard

http://www.d6.com/users/checker/pdfs/gdmfp.pdf

Just keep in mind that the bit patterns presented does not necessarily

directly correspond to the in-memory patterns used by the Java VM.

The only thing that is guaranteed is that the externally visible effect

of the mathematical operations are identical to the ones specified

by IEEE 754.

"Plurality should not be posited without necessity."<br /> William of Ockham