Question about data types

[Cheyne Cadwallader]

I'm new to c++ and I am only a beginner programmer with experience in C, Javascript, TI-BASIC and C++ so please forgive my newbishness.

I was wondering, how come there are different data-types that represent the same values? In the book I'm working through it explains the data types as follows:

INT = 4 bytes
Short Int = 2 bytes
Long Int = 4 bytes
Char = 1 byte
boole = 1 byte
float = 4 bytes
double float = 8 bytes
Long long int = 8 bytes

So like with INT and Long int. They take up exactly the same amount of space and they are both integers. How come they need two different categories?

[JLBorges]

The number of bytes used in the object representation of, say, int is implementation-defined. All that C++ requires is that long int can't be narrower than int, and can't be wider than long long int etc.

#include <iostream>

int main() 
{
    std::cout << "      sizeof(short): " << sizeof(short) << '\n'
              << "        sizeof(int): " << sizeof(int) << '\n'
              << "       sizeof(long): " << sizeof(long) << '\n'
              << "  sizeof(long long): " << sizeof(long long) << '\n' ;
              
    std::cout << "      sizeof(float): " << sizeof(float) << '\n'
              << "     sizeof(double): " << sizeof(double) << '\n'
              << "sizeof(long double): " << sizeof(long double) << '\n' ;
}

On one implementation:

      sizeof(short): 2
        sizeof(int): 4
       sizeof(long): 8
  sizeof(long long): 8
      sizeof(float): 4
     sizeof(double): 8
sizeof(long double): 16

http://coliru.stacked-crooked.com/a/fb3e9214f1feeb54

On another:

      sizeof(short): 2
        sizeof(int): 4
       sizeof(long): 4
  sizeof(long long): 8
      sizeof(float): 4
     sizeof(double): 8
sizeof(long double): 8

http://rextester.com/OGB65684

For fixed-width integer types like std::int32_t, see: http://en.cppreference.com/w/cpp/header/cstdint

[ModShop]

It depends on the platform's implementation of the data type. The standard dictates that sizeof(long int)>=sizeof(int), therefor it is perfectly possible for them to have the same size. On some platforms, however, you could also have long int be longer than int

edit: ninja'd :/