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.
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)
Other Built in types
bool
|
Boolean ( True or False )
|
void
|
Without any Value
|
wchar_t
|
Wide Character
|
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.
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, which is always positive.
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