What is the difference between int, Int16, Int32 and Int64?

According to Jeffrey Richter(one of the contributors of .NET framework development)'s book 'CLR via C#':

int is a primitive type allowed by the C# compiler, whereas Int32 is the Framework Class Library type (available across languages that abide by CLS). In fact, int translates to Int32 during compilation.

Also,

In C#, long maps to System.Int64, but in a different programming language, long could map to Int16 or Int32. In fact, C++/CLI does treat long as Int32.

In fact, most (.NET) languages won't even treat long as a keyword and won't compile code that uses it.

I have seen this author, and many standard literature on .NET preferring FCL types(i.e., Int32) to the language-specific primitive types(i.e., int), mainly on such interoperability concerns.

The only real difference here is the size. All of the int types here are signed integer values which have varying sizes

• Int16: 2 bytes
• Int32 and int: 4 bytes
• Int64 : 8 bytes

There is one small difference between Int64 and the rest. On a 32 bit platform assignments to an Int64 storage location are not guaranteed to be atomic. It is guaranteed for all of the other types.

Each type of integer has a different range of storage capacity

   Type      Capacity

   Int16 -- (-32,768 to +32,767)

   Int32 -- (-2,147,483,648 to +2,147,483,647)

   Int64 -- (-9,223,372,036,854,775,808 to +9,223,372,036,854,775,807)

As stated by James Sutherland in his answer:

int and Int32 are indeed synonymous; int will be a little more familiar looking, Int32 makes the 32-bitness more explicit to those reading your code. I would be inclined to use int where I just need 'an integer', Int32 where the size is important (cryptographic code, structures) so future maintainers will know it's safe to enlarge an int if appropriate, but should take care changing Int32 variables in the same way.

The resulting code will be identical: the difference is purely one of readability or code appearance.

int

It is a primitive data type defined in C#.

It is mapped to Int32 of FCL type.

It is a value type and represent System.Int32 struct.

It is signed and takes 32 bits.

It has minimum -2147483648 and maximum +2147483647 value.

Int16

It is a FCL type.

In C#, short is mapped to Int16.

It is a value type and represent System.Int16 struct.

It is signed and takes 16 bits.

It has minimum -32768 and maximum +32767 value.

Int32

It is a FCL type.

In C#, int is mapped to Int32.

It is a value type and represent System.Int32 struct.

It is signed and takes 32 bits.

It has minimum -2147483648 and maximum +2147483647 value.

Int64

It is a FCL type.

In C#, long is mapped to Int64.

It is a value type and represent System.Int64 struct.

It is signed and takes 64 bits.

It has minimum –9,223,372,036,854,775,808 and maximum 9,223,372,036,854,775,807 value.