Unlike python, which understands the type of data on its own,
C++ compiler needs complete information about the type of values that can be
stored in a variable. This type is defined using datatypes. Once the
type of variable is defined, compiler knows what space the variable would take
and what operations are allowed on that variable.
DATATYPES IN C++
1.
Primitive/ Fundamental
2.
Derived
3.
User defined
Read more >>
This article here discusses Primitive data types.
Primitive data types or Fundamental
data types are those that are not composed of other data types. They are
individual entities having predefined characteristics of their own.
6 mostly used primitive datatypes have been discussed
below :
1.
Integer data type (int) : The
keyword for integer data type is int. Integers are numbers without
fractional parts. They occupy 4 bytes space in memory (according to latest
Compilers). It is the most widely used data type in any computer program
because of its moderate range and less space consumption.
2.
Character data type (char) : The
keyword for character data type is char. A character type variable can
store any value from the C++ character set.
Character variables are basically integer types which trigger the compiler
differently. Any character stored in the variable is stored as its ASCII value
which is an integer. A character variable occupies 1 byte of space in memory.
Read more >> Character set in C++
3.
Boolean data type (bool) : The
keyword for Boolean data type is bool. A Boolean variable is used to
store relational and logical values. It can store either true or false. It
occupies 1 byte of space in memory.
4.
Floating point (float) : The
keyword for floating point data type is float. They are used to store
real (i.e. decimal point) numbers. They have a size of 4 bytes and are less
precise than double.
5.
Double data type (double) : The
keyword used for double data types is double. They also store real
numbers but with greater precision (i.e. more significant figures) than float.
They take 8 bytes of space in memory.
6.
Void data type (void) : The
keyword used for void datatype is void. It is used to denote “nothing”
or a valueless entity. As it doesn’t store any value, it takes no space
in the memory.
DATATYPE MODIFIERS
Except type void, the basic datatypes may have various
modifiers preceding them. As the name implies, a modifier can be used to alter
the meaning of the base type to fit various situations more precisely.
The list of modifiers is : signed, unsigned, long, short
As shown in the above diagram, we can apply signed, unsigned,
long and double to int and signed, unsigned to char. However, we may also apply long
to double. (Note that ANSI doesn’t allow for long float as it is
nothing but double).
Let us discuss the modifiers in detail:
Integer types:
By using different number of bytes to store values, C++ offers
three types of integers: short, int and long that can represent
three different integer sizes. Each comes in both signed and unsigned format.
That gives us a total of 6 of integer types. The sizes can vary from compiler
to compiler but C++ offers a flexible standard with some guaranteed minimum
sizes as:
A short integer is at least 2 bytes.
An int integer is at least as big as short.
A long integer is at least 4 bytes and at least as big
as int.
|
Type |
Approx size (in bytes) |
Minimal Range |
|
short unsigned
short signed
short |
2 2 2 |
-32768 to
32767 0 to 65535 same as
short |
|
int unsigned
int signed int |
4 4 4 |
-(231)
to +(231)-1 0 to (232)-1 same as
int |
|
long unsigned
long signed
long |
4 4 4 |
same as
int same as
unsigned int same as
int |
Note : It is obvious from the table that short,
int, long are signed by default. Also, the C++11 update also
provides for a type long long int with size of at least 8 bytes.
Character Types:
The char type is really another integer type (as inside memory
it actually holds numbers i.e. ASCII of the characters). It is guaranteed to be
large enough to represent the entire character set of 256 characters. As we
know 1 byte space holds a total of 256 numbers, therefore all char types have size
of 1 byte.
|
Type |
Approx Size (in byte) |
Minimal Range |
|
char unsigned
char signed
char |
1 1 1 |
-128 to
127 0 to 255 same as
char |
Floating-point Types:
C++ has 3 floating types : float, double, long double. These
are defined by the number of significant figures that they can hold (i.e. precision).
|
Types |
Approx Size (in bytes) |
Minimal Range |
Digits of precision |
|
float double long double |
4 8 10 |
3.4 x 10-38 to 3.4 x 1038 -1 1.7 x 10-308 to 1.7 x 10308-1 3.4 x 10-4932 to 3.4 x 104932 -1 |
7 15 19 |
The sizeof() Operator:
The size allotted to variables of different types are different. Also, the size of same type of variable can be different for different compilers. To cope with this difficulty, C++ provides an inbuilt function sizeof(data_type), which returns the size of the data type in bytes.
Output Screen :
Size of char is 1
Size of int is 4
Size of long int is 4
Size of long long int is 8
Size of float is 4
Size of double is 8
Size of long double is 16
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