Data Types

What are data type? Data types are those classified keywords which defines the type of variable or the nature of variable.  Although there are many data types but usually there are four primitive built-in datatypes which are regularly used by programmer in a programming language namely:

1. Integer         (int)
2. Float           (float)
3. Double        (double)
4. Characters  (char)

While doing programming in any programming language, you need to use various variables to store various information. Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in memory.
You may like to store information of various data type like character, wide character, integer, floating point, double floating point, boolean etc. Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the reserved memory. Along with the datatypes modifiers can be prefixed as per the requirement of the program. You must be  wondering what are these modifiers. Modifiers are those keywords which precedes the data types. Some of the basic modifiers are unsigned, signed, long, short, etc. These may or may not be compatible with some of the datatypes.

These are some issues regarding the incompatibility of the modifiers with some datatypes like long and short modifiers can not be used with char datatype. So here are some key points which beginner or a programmer must always remember:

• long and short modify the maximum and minimum values that a data type will hold.
• A plain int must have a minimum size of short.
• Size hierarchy : short int < int < long int
• Size hierarchy for floating point numbers is : float < double < long double
• long float is not a legal type and there are no short floating point numbers.
• Signed types include both positive and negative numbers and is a default type.
• Unsigned, numbers are always without any sign, that is always positive.

Here is the list of all the possible data types which are used by a programmer (rookie/expert/professional ) on a regular basis.

Datatype	Modifier(Signed/unsigned)	Modifier(Long/Short)	Basic Data Type	size of data type
int	Default	Default	int	4
long	Default(signed)	long	Default(int)	4
short	Default(signed)	short	Default(int)	2
signed	signed	Default	Default(int)	4
unsigned	unsigned	Default	Default(int)	4
signed short	signed	short	Default(int)	2
unsigned short	unsigned	short	Default(int)	2
signed long	signed	long	Default(int)	4
unsigned long	unsigned	long	Default(int)	4
long signed int	signed	long	int	4
long unsigned int	unsigned	long	int	4
short signed int	signed	short	int	2
short unsigned int	unsigned	short	int	2
Short int	Default(signed)	short	int	2
long int	Default(signed)	long	int	4
long long	Default(signed)	long long	int	8
long long int	Default(signed)	long long	int	8
long long signed int	Default(signed)	long long	int	8
long long unsigned int	Default(signed)	long long	int	8
long long signed	Default(signed)	long long	int	8
long long unsigned	Default(signed)	long long	int	8
signed int	signed	Default	int	4
unsigned int	unsigned	Default	int	4
char	Default(signed)	Default	char	1
signed char	signed	Default	char	1
unsigned char	unsigned	Default	char	1
float	Default	Default	float	4
long float	Default	long	float	8
double	Default	Default	double	8
long double	Default	long	double	8
bool	Default	Default	Default	1
int*	Default	Default	int*	4
char*	Default	Default	char*	4
float*	Default	Default	float*	4
double*	Default	Default	double*	4
wchar_t	Default	Default	wchar_t	2
short *	Default	Default	int *	4
long*	Default	Default	int *	4
signed*	Default(signed)	Default	int *	4
unsigned *	unsigned	Default	int *	4

The above table shows the variable type, modifiers and there cases of implementing with datatypes, Basic data types and how much memory it takes to store the value memory. 

The size of the above given data types may vary from machine to machine. So to see the correct size of various data type on your computer the following program coded in C++ may try help you to get an idea of the size of your datatype used by your computer:

#include <iostream>

using namespace std;

int main()

{

   cout << "Size of char : " << sizeof(char) << endl;

   cout << "Size of int : " << sizeof(int) << endl;

   cout << "Size of short int : " << sizeof(short int) << endl;

   cout << "Size of long int : " << sizeof(long int) << endl;

   cout << "Size of float : " << sizeof(float) << endl;

   cout << "Size of double : " << sizeof(double) << endl;

   cout << "Size of wchar_t : " << sizeof(wchar_t) << endl;

   return 0;

}

This example uses endl which inserts a new-line character after every line and << operator is being used to pass multiple values out to the screen. We are also using sizeof() function to get size of various data types.

When the above code is compiled and executed, it produces following result which can vary from machine to machine:

Size of char : 1

Size of int : 4

Size of short int : 2

Size of long int : 4

Size of float : 4

Size of double : 8

Size of wchar_t : 2