Question

Correct me if I am wrong,

int is 4 bytes, with a range of values from -2,147,483,648 to 2,147,483,647 (2^31)
long is 4 bytes, with a range of values from -2,147,483,648 to 2,147,483,647 (2^31)

What is the difference in C++? Can they be used interchangeably?

Answer 1

It is implementation dependent.

For example, under Windows they are the same, but for example on Alpha systems a long was 64 bits whereas an int was 32 bits. This article covers the rules for the Intel C++ compiler on variable platforms. To summarize:

  OS           arch           size Windows       IA-32        4 bytes Windows       Intel 64     4 bytes Windows       IA-64        4 bytes Linux         IA-32        4 bytes Linux         Intel 64     8 bytes Linux         IA-64        8 bytes Mac OS X      IA-32        4 bytes Mac OS X      Intel 64     8 bytes