Newbie 4 Byte Question

[ThomasIngold]

Hi !

In a programming lesson we had the following :
a)"What's the highest value that can be stored within a 4-Byte float ?"

answer: (2^31)-1.

Why is it not 2^32 ?
Or why is it not (2^32)-1 ??



b)"What's the smallest value that can be stored within a 4-Byte float ?"

answer: -2^31

???


Can anybody help me with that ?
btw i know that 4 Byte are 32 Bit

Thanks
Tom

[Krushstone]

Are you really talking about floats? floating point numbers?

I'm asking this because the max value for a single precision floating point number is
3.402823E38
which isn't related to 2^32 in any way...

Are you sure you're not talking about 4 byte integers? (long or double depending on the language)

[Zaei]

Yeah, if dealing with real floating point values, its wrong. if dealing with integer values:

The answer is because you are using a signed value. 4 bytes == 32 bits. If you were to use all 32 bits, you would have 2^32. But, since you are using a signed value, one bit is used as the sign bit, leaving only 31 bits, 2^31. The -1 comes from the fact that 0 is positive, so you cannot store the value 2^31. Since 0 is not negative, you CAN store -2^31.

Z.

[Zaei]

In what language is a double an integer value?

Z.

[The Hobo]

Originally posted by Zaei
In what language is a double an integer value?

Z.

Spanish.

[ThomasIngold]

Thanks Zaei !

I can understand now ! Cool !!

He really asked for a 4Byte float - checked it again !
Don't know if he refered to C++ ? (What we're doing )

Thanks !