Overview

The fundamental data types in C++ are the basic building blocks for creating other data types. There are five basic classifications that form the foundation of the fundamental types: characters, integers, floating-point numbers, booleans, and the void type.

Characters

The character type has two basic variants: one of ACSII characters and one for Unicode characters. The char type is used to store 8 bit characters according to the specification in the ASCII table. The wchar_t type is used to store 16 bit characters according to the Unicode specification for UTF 16. The actual values stored in these data types are integers whose values are seldom used directly. However, due to the legacy usage of C/C++, there are three specifications for the char type: char, signed char, and unsigned char

Integers

The integer type has three distinct sizes: 16 bit, 32 bit and 64 bit. You could also add in the char type as an 8 bit variant. Each different size can store a corresponding range of integer values and each has a signed and unsigned variant. Many of these have multiple names that can be used to specify it.

Floating-Point Numbers

The floating point number type has two distinct sizes: 32 bit and 64 bit. The 32 bit variant is specified by the name float and the 64 bit number is specified by the name double. The double has uses twice the memory to give a range of values and greater precision. As memory in computers has grown, the float type has fallen out of usage in numerical programming, and virtually everyone uses the double type now.

Booleans

The only Boolean type is the bool data type. This is used to represent the two logical values true and false.

Void

There is one Void type called void, it is not really a data type at all. It is used to specify that no type is used. Otherwise, it can be used as a pointer type to indicate that the type is unknown.

Fundamental Types

Category	Type	Range	Size *
Character	char	[-128, 127]	1 byte
	signed char	[-128, 127]	1 byte
	unsigned char	[0,255]	1 byte
	wchar_t	[0, 65535]	2 bytes
Integer
	short	[-32768, 32767]	2 bytes
	short int	[-32768, 32767]	2 bytes
	signed short int	[-32768, 32767]	2 bytes
	signed	[-2147483648, 2147483647]	4 bytes
	signed int	[-2147483648, 2147483647]	4 bytes
	int	[-2147483648, 2147483647]	4 bytes
	long	[-2147483648, 2147483647]	4 bytes
	long int	[-2147483648, 2147483647]	4 bytes
	signed long int	[-2147483648, 2147483647]	4 bytes
	long long	[-9223372036854775808, 9223372036854775807]	8 bytes
	unsigned short	[0, 65535]	2 bytes
	unsigned short int	[0, 65535]	2 bytes
	unsigned	[0, 4294967295]	4 bytes
	unsigned int	[0, 4294967295]	4 bytes
	unsigned long	[0, 4294967295]	4 bytes
	unsigned long int	[0, 4294967295]	4 bytes
	unsigned long long	[0, 18446744073709551615]	8 bytes
Floating Point
	float	[-3.4*10^38, 3.4*10^38] (7 decimal place accuracy)	4 bytes
	double	[-1.7*10^308, 1.7*10^308] (15 decimal place accuracy)	8 bytes
	long double	[-1.7*10^308, 1.7*10^308] (15 decimal place accuracy)	8 bytes
Boolean	bool	{true, false}	1 byte
Void	void	—	—

Note: The sizes above are Visual C++-specific. Other compilers may vary, but the relationships in the Guaranteed Size Relationships section always hold.

Guaranteed Size Relationships

	1 = sizeof(char) <= sizeof(short) <= sizeof(int) <= sizeof(long)
	1 <= sizeof(bool) <= sizeof(long)
	sizeof(char) <= sizeof(wchar_t) <= sizeof(long)
	sizeof(float) <= sizeof(double) <= sizeof(long double)
	sizeof(N) = sizeof(signed N) = sizeof(unsigned N)