Is an int a 64-bit integer in 64-bit C#?

Question

In my C# source code I may have declared integers as:

int i = 5; 

or

Int32 i = 5; 

In the currently prevalent 32-bit world they are equivalent. However, as we move into a 64-bit world, am I correct in saying that the following will become the same?

int i = 5; Int64 i = 5; 

Answer 1

No. The C# specification rigidly defines that int is an alias for System.Int32 with exactly 32 bits. Changing this would be a major breaking change.

Answer 2

The int keyword in C# is defined as an alias for the System.Int32 type and this is (judging by the name) meant to be a 32-bit integer. To the specification:

CLI specification section 8.2.2 (Built-in value and reference types) has a table with the following:

• System.Int32 - Signed 32-bit integer

C# specification section 8.2.1 (Predefined types) has a similar table:

• int - 32-bit signed integral type

This guarantees that both System.Int32 in CLR and int in C# will always be 32-bit.