What is are some usages of fixed width integer types in c++?

Question

I just discovered these fixed width integer types while experimenting. For example Int32 or Int64. In what situation would one want to use one or the other?

Answer 1

Precise sized integers are used in cryptographic functions. This is so the function can exactly follow a specification.
Example: md5 checksum.

Answer 2

Do you know any examples?