What does the C++ standard state the size of int, long type to be?

Question

I\'m looking for detailed information regarding the size of basic C++ types. I know that it depends on the architecture (16 bits, 32 bits, 64 bits) and the compiler.

Answer 1

From Alex B The C++ standard does not specify the size of integral types in bytes, but it specifies minimum ranges they must be able to hold. You can infer minimum size in bits from the required range. You can infer minimum size in bytes from that and the value of the CHAR_BIT macro that defines the number of bits in a byte (in all but the most obscure platforms it's 8, and it can't be less than 8).

One additional constraint for char is that its size is always 1 byte, or CHAR_BIT bits (hence the name).

Minimum ranges required by the standard (page 22) are:

and Data Type Ranges on MSDN:

signed char: -127 to 127 (note, not -128 to 127; this accommodates 1's-complement platforms) unsigned char: 0 to 255 "plain" char: -127 to 127 or 0 to 255 (depends on default char signedness) signed short: -32767 to 32767 unsigned short: 0 to 65535 signed int: -32767 to 32767 unsigned int: 0 to 65535 signed long: -2147483647 to 2147483647 unsigned long: 0 to 4294967295 signed long long: -9223372036854775807 to 9223372036854775807 unsigned long long: 0 to 18446744073709551615 A C++ (or C) implementation can define the size of a type in bytes sizeof(type) to any value, as long as

the expression sizeof(type) * CHAR_BIT evaluates to the number of bits enough to contain required ranges, and the ordering of type is still valid (e.g. sizeof(int) <= sizeof(long)). The actual implementation-specific ranges can be found in header in C, or in C++ (or even better, templated std::numeric_limits in header).

For example, this is how you will find maximum range for int:

C:

#include 
const int min_int = INT_MIN;
const int max_int = INT_MAX;

C++:

#include 
const int min_int = std::numeric_limits::min();
const int max_int = std::numeric_limits::max();

This is correct, however, you were also right in saying that: char : 1 byte short : 2 bytes int : 4 bytes long : 4 bytes float : 4 bytes double : 8 bytes

Because 32 bit architectures are still the default and most used, and they have kept these standard sizes since the pre-32 bit days when memory was less available, and for backwards compatibility and standardization it remained the same. Even 64 bit systems tend to use these and have extentions/modifications. Please reference this for more information:

http://en.cppreference.com/w/cpp/language/types