Question

C99 states integer types like uint32_t, int16_t etc, where it’s easy to see the number of bits used. Good to know in for instance embedded programming.

I have not found any similar types for floating point values. Is there a standard? If not, why?

Answer 1

I found the answer in Any guaranteed minimum sizes for types in C?

Quoting Jed Smith (with corrected link to C99 standard):

Yes, the values in float.h and limits.h are system dependent. You should never make assumptions about the width of a type, but the standard does lay down some minimums. See §6.2.5 and §5.2.4.2.1 in the C99 standard.

For example, the standard only says that a char should be large enough to hold every character in the execution character set. It doesn’t say how wide it is.

For the floating-point case, the standard hints at the order in which the widths of the types are given:

§6.2.5.10

There are three real floating types, designated as float, double, and long
double. ³²) The set of values of the type float is a subset of the set of values of the type double; the set of values of the type double is a subset of the set of values of the type long double.

They implicitly defined which is wider than the other, but not specifically how wide they are. “Subset” itself is vague, because a long double can have the exact same range of a double and satisfy this clause.

This is pretty typical of how C goes, and a lot is left to each individual environment. You can’t assume, you have to ask the compiler.