unsigned short vs unsigned int - sometimes they are the same range? [closed]

Question

What's the difference between unsigned short and unsigned int? I found that unsigned short is 0-65,535 and unsigned int is 0-65,535 or 0-4,294,967,295. I don't understand the difference very well. How can I know the size of data type in my architecture? And if for example c = (unsigned short) d; when c is an unsigned short and d is an unsigned int ; what is that mean? the first 16 bits from d are assigned to c?

Answer 1

This is a useful link to explain the history of C data types:

http://en.wikipedia.org/wiki/C_data_types

So the size of your data type is platform-dependent, but if your int is 32-bits in length then it will be able to represent one of 2^32 different numbers (0 - 4,294,967,295 if unsigned). Similarly if your short is 16-bits in length then it can represent one of 2^16 different numbers (0 - 65,535 if unsigned).

This link gives you the implementation details for Visual Studio 2005, where ints are 32-bits in size (4 bytes) and shorts are 16-bits (2 bytes):

http://msdn.microsoft.com/en-us/library/s3f49ktz(v=vs.80).aspx

Your exact implementation will depend on your compiler.

As for the last part of your question, yes if you attempt to cast down an int larger than the short's maximum value to a short then you will end up with a different value (probably the first 16 bits but you should test to be sure).

Answer 2

You're really asking what is the difference between short and int. The answer is that short may be narrower, but may also be the same width as, int. That's virtually all we know for sure, independent of platform. A lot of platforms have 32-bit int and 16-bit short, but not all.