Data types and Modifiers in C++ ~ GNIITHELP

Data Types in C++

They are used to define type of variables and contents used. Data types define the way you use storage in the programs you write. Data types can be built in or abstract.

Built in Data Types

These are the data types which are predefined and are wired directly into the compiler. eg: int, char etc.

User defined or Abstract data types

These are the type, that user creates as a class. In C++ these are classes where as in C it was implemented by structures.

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Basic Built in types

char	for character storage ( 1 byte )
int	for integral number ( 2 bytes )
float	single precision floating point ( 4 bytes )
double	double precision floating point numbers ( 8 bytes )

Example :

char a = 'A';          // character type
int a = 1;             // integer type
float a = 3.14159;     // floating point type 
double a = 6e-4;       // double type (e is for exponential)

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Other Built in types

bool	Boolean ( True or False )
void	Without any Value
wchar_t	Wide Character

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Enum as Data type

Enumerated type declares a new type-name and a sequence of value containing identifiers which has values starting from 0 and incrementing by 1 every time.

For Example :

enum day(mon, tues, wed, thurs, fri) d;

Here an enumeration of days is defined with variable d. mon will hold value 0, tue will have 1 and so on. We can also explicitly assign values, like, enum day(mon, tue=7, wed);. Here, mon will be 0, tue is assigned 7, so wed will have value 8.

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Modifiers

Specifiers modify the meanings of the predefined built-in data types and expand them to a much larger set. There are four data type modifiers in C++, they are :

1. long
2. short
3. signed
4. unsigned

Below mentioned are some important points you must know about the modifiers,

• 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 includes both positive and negative numbers and is the default type.
• Unsigned, numbers are always without any sign, that is always positive.