Question

I am new to programming, I’ve done web development, but I am currently trying to learn real programming. The question I have is already answered here.

union ufloat {
  float f;
  unsigned u
};

ufloat u1;
u1.f = 0.3f;

What I don’t get is how it works. What does the 0.3 part do? I couldn’t find it in my text. And how does this convert a float to binary? Because cout<<u1.u; doesn’t seem to give me the answer. Can someone help?

Answer 1

0.3 is just a test value. Printing u1.u will not give you the binary representation, but the value of the binary representation interpreted as a base 10 integer. To get the binary value, you have to convert u1.u to binary.

Another way you can do the conversion is by using bitwise operators.

For example:

unsigned x = 11;
do
{
    cout << (x & 1); // print last bit
    x = x >> 1; // get rid of the printed bit
} while ( x );

Note that this will print the bits in reverse order (least significant first). I’ll leave it up to you to fix this (you can use recursion or store values in an array and then print the array reversed).

I also suggest you read about unions. Basically, the unsigned will occupy the same memory space as the float, allowing you to circumvent the restrictions of using bitwise operators to find the binary representation of the float.