Float to Hex

[fidelcashflo]

Hello, I am trying to write a program that converts a floating point number into IEEE 32 and IEEE 64 bit hexadecimal representation. To do this, I can not use any built in converting functions of C++.

I was wondering if someone could show me a function that takes in an char array(max size 256) and prints the hexadecimal representation of that floating number. The number can be a negative or a positive.

For example:

Floating number = -0.25
IEEE 32 = BE800000
IEEE 64 = BFD0000000000000

I'm just looking for a way to get started. So any help will be appreciated. Thank you.

[webJose]

The question "number to hex" has been answered multiple times in this and other forums. I find it surprising that a Google search wouldn't give you the answer. For example: http://bit.ly/HUnDiM . Second result seem to point to the simplest way of doing this in C++.

[Stewbond]

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#include <iostream> #include <iomanip> union ufloat { float f; unsigned long u; }; union udoub { double d; unsigned long long u; }; int main() { ufloat a; udoub b; a.f = -0.25f; b.d = -0.25; std::cout << std::setw(8) << std::setfill('0') << std::hex << a.u << std::endl; std::cout << std::setw(16)<< std::setfill('0') << std::hex << b.u << std::endl; return 0; }

be800000 bfd0000000000000 Press any key to continue . . .

[fidelcashflo]

Thank you guys for the response.

The reason I am having trouble with this program is because we are not allowed to use such functions as "hex", "atof()", "%x" or any built in class functions.

So, if anybody could set me in the right direction on how to go about doing this, that would greatly appreciated.

[Stewbond]

Well in that case, the code above at least gives you a unsigned int. That's 70% done. From there it isn't too hard to convert to hex values.