Does double have a greater range than long?

Question

In an article on MSDN, it states that the double data type has a range of "-1.79769313486232e308 .. 1.79769313486232e308". Whereas the long data type only has a range of "-9,223,372,036,854,775,808 .. 9,223,372,036,854,775,807". How can a double hold so much more data than a long if they are both 64 bits in size?

http://msdn.microsoft.com/en-us/library/cs7y5x0x(v=vs.90).aspx

Answer 1

The number of possible doubles, and the number of possible longs is the same, they are just distributed differently*.

The longs are uniformly distributed, while the floats are not. You can Read more here .

I'd write more, but for some reason the cursor is jumping around all over the place on my phone.

Edit: This might actually be more helpful: http://en.wikipedia.org/wiki/Double-precision_floating-point_format#section_1

Edit2: and this is even better: http://blogs.msdn.com/b/dwayneneed/archive/2010/05/07/fun-with-floating-point.aspx

* According to that link, it would seem that there are actually more longs, since some doubles are lost due to the way NaNs and other special numbers are represented.

Answer 2

long is a signed 64-bit integer value and double is a 64-bit floating point value. Looking at their FCL types might make more sense. long maps to System.Int64 and double maps to System.Double .

Answer 3

A simple answer is that double is only accurate to 15-16 total digits, as opposed to long which (as an integer type) has an absolute accuracy within an explicit digit limit , in this case 19 digits. (Keep in mind that digits and values are semantically different.)

double : -/+ 0.000,000,000,000,01 to +/- 99,999,999,999,999.9 (at 100% accuracy, with a loss in accuracy starting from 16th digit, as represented in "-1.79769313486232e308 .. 1.79769313486232e308".)

long : -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807

ulong : 0 to 18,446,744,073,709,551,615 (1 more digit than long, but identical value range (since it's only been shifted to exclude negative returns).

In general, int-type real numbers are preferred over floating-point decimal values , unless you explicitly need a decimal representation (for whichever purpose).

---

In addition, you may know that signed are preferred over unsigned , since the former is much less bug-prone (consider the statement uint i; , then i - x; where x > i ).