In C++, the size and range of integer types depend on the compiler and the platform it runs on, but some basic rules are generally followed. long, long long, long int, and long long int are types primarily used for integers, but they have different sizes and ranges.
1. long and long int
In C++, long and long int are the same type and can be used interchangeably. Typically, long is at least as large as int. On many platforms, long is a 32-bit integer type, but on some 64-bit systems, long may be 64-bit. For example, on 64-bit Linux and Mac OS X, long is typically 64-bit, whereas on Windows platforms, whether 32-bit or 64-bit, long is generally 32-bit.
2. long long and long long int
long long and long long int are the same type and can be used interchangeably. This type in C++ provides at least 64-bit integer precision. It is designed to provide a type with sufficient integer range across all platforms, especially useful when handling very large numbers, such as in financial analysis or scientific computing.
Example
Suppose we need to process identity identifiers for all people globally, which consist of very large numbers. In this case, using int or long may not suffice because their maximum values may not be sufficient to represent so many unique identifiers. Using the long long type is appropriate here, as it provides at least 64-bit storage, with a representable range far exceeding that of long.
Conclusion
When choosing these types, it is important to consider the size and range of data your application needs to handle. If you know the values won't be particularly large, using int or long may be sufficient. However, if you anticipate handling very large values, choosing long long will be a safer choice to avoid potential integer overflow issues.