C++ Datatypes
The basic built in data types are char, int, float,
double and void.
Type |
Keyword |
|
|
Character |
char |
|
|
Integer |
int |
|
|
Floating point |
float |
|
|
Double floating point |
double |
|
|
Valueless |
void |
Integer data type: these
are the numbers without having decimal point that may (or) may not
prefixed with a ‘-‘ (or) ‘+’ sign. Ex: 234, -765.
Float data type: these are the numbers with decimal points value. In C++ floats are stored with 6 digits of decimal precession. Ex: 9.67 , 897.567,….
Character data type: A single character is enclosed with single quotes can be defined as a character data type. Ex: ‘n’ , ‘d’, …..
Void data type: it is the latest addition to C++, it is value less (or) null data type.
Several of the basic types can be modified using one or more of these type modifiers:
- signed
- unsigned
- short
- long
The following table shows the variable type, how much memory it takes
to store the value in memory, and what is maximum and minimum value which can
be stored in such type of variables.
|
Type |
|
|
Length |
|
|
Range |
|
|
|
char |
|
1byte |
|
-128 to 127 or 0 to 255 |
|
|||
|
unsigned char |
|
1byte |
|
0 to 255 |
|
|||
|
signed char |
|
1byte |
|
-128 to 127 |
|
|||
|
int |
|
4bytes |
|
-2147483648 to 2147483647 |
|
|||
|
unsigned int |
|
4bytes |
|
0 to 4294967295 |
|
|||
|
signed int |
|
4bytes |
|
-2147483648 to 2147483647 |
|
|||
|
short int |
|
2bytes |
|
-32768 to 32767 |
|
|||
|
unsigned short |
|
2bytes |
|
0 to 65,535 |
|
|||
|
int |
|
|
|
|
|
|
|
|
|
signed short int |
|
2bytes |
|
-32768 to 32767 |
|
|||
|
long int |
|
4bytes |
|
-2,147,483,648 to 2,147,483,647 |
|
|||
|
signed long int |
|
4bytes |
|
-2,147,483,648 to 2,147,483,647 |
|
|||
|
unsigned long |
|
4bytes |
|
0 to 4,294,967,295 |
|
|||
|
int |
|
|
|
|
|
|
|
|
|
float |
|
4bytes |
|
+/- 3.4e +/- 38 (~7 digits) |
|
|||
|
double |
|
8bytes |
|
+/- 1.7e +/- 308 (~15 digits) |
|
|||
|
long double |
|
8bytes |
|
+/- 1.7e +/- 308 (~15 digits) |
|
Derived Data types
The data-types
that are derived from the primitive or built-in datatypes are referred to as
Derived Data Types. These can be of four types namely:
- Function
- Array
- Pointers
- Reference
1. Function :
A function is a
block of code or program-segment that is defined to perform a specific
well-defined task. A function is generally defined to save the user from
writing the same lines of code again and again for the same input. All the
lines of code are put together inside a single function and this can be called
anywhere required. main() is a default function that is defined in every
program of C++.
FunctionType FunctionName(parameters)
{
// function
body;
}
2. Array :
An array is a
collection of items stored at continuous memory locations. The idea of array is
to represent many instances in one variable.
Syntax:
DataType ArrayName[size_of_array];
Ex: int
a[5];
3. Pointer :
Pointers are
symbolic representation of addresses. They enable programs to simulate
call-by-reference as well as to create and manipulate dynamic data structures.
It’s general declaration in C is:
datatype *var_name;
Ex: int
*ptr;
4. Reference
A reference
variable is an alias, that is, another name for an already existing variable.
Once a reference is initialized with a variable, either the variable name or
the reference name may be used to refer to the variable.
Example:
int i=10;
int &R = i;
References are
often confused with pointers but three major differences between references and
pointers are −
- You cannot have NULL references.
You must always be able to assume that a reference is connected to a
legitimate piece of storage.
- Once a reference is initialized to
an object, it cannot be changed to refer to another object. Pointers can
be pointed to another object at any time.
- A reference must be initialized
when it is created. Pointers can be initialized at any time.
User defined datatypes:
C++ allows
programmers to define their identifier that would represent an existing data
type. There are three such types:
•
Structure
•
Union
•
enum
•
class
1. Structure:
It is a package
of variables of different types under a single name. This is done to handle
data efficiently. "struct" keyword is used to define a structure.
struct
[structure tag] {
member definition;
member definition;
...
member definition;
} [one or more
structure variables];
Ex:
struct Books {
char
title[50];
char
author[50];
char
subject[100];
int
book_id;
} book;
2. Union:
These allow
storing various data types in the same memory location. Programmers can define
a union with different members, but only a single member can contain a value at
a given time.
union [union
tag] {
member definition;
member definition;
...
member definition;
} [one or more
union variables];
Ex:
union Data {
int i;
float f;
char str[20];
} data;
3. enum:
Enumeration is a
special data type that consists of integral constants, and each of them is
assigned with a specific name. "enum" keyword is used to define the
enumerated data type.
Variables of
type enum can also be defined. They can be defined in two ways:
// In both of
the below cases, "day" is
// defined as
the variable of type week.
enum week{Mon,
Tue, Wed};
enum week day;
// Or
enum week{Mon,
Tue, Wed}day;
4. class:
A class is a
user-defined data type. A class is used to specify the form of an object and it
combines data representation and methods for manipulating that data into one
neat package. The data and functions within a class are called members of the
class.
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