The basic in any programming language is the variables where you store the data. 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 types in c++ 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.
Primitive Built-in Types:
Type | Keyword |
---|---|
Boolean | bool |
Character | char |
Integer | int |
Floating point | float |
Double floating point | double |
Valueless | void |
Wide character | wchar_t |
Several of the basic types can be modified using one or more of these type modifiers:
- signed
- unsigned
- short
- long
Size of each Data Type:
Type | Typical Bit Width | Typical Range |
---|---|---|
char | 1byte | -127 to 127 or 0 to 255 |
unsigned char | 1byte | 0 to 255 |
signed char | 1byte | -127 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 int | Range | 0 to 65,535 |
signed short int | Range | -32768 to 32767 |
long int | 4bytes | -2,147,483,647 to 2,147,483,647 |
signed long int | 4bytes | same as long int |
unsigned long int | 4bytes | 0 to 4,294,967,295 |
float | 4bytes | +/- 3.4e +/- 38 (~7 digits) |
double | 8bytes | +/- 1.7e +/- 308 (~15 digits) |
long double | 8bytes | +/- 1.7e +/- 308 (~15 digits) |
wchar_t | 2 or 4 bytes | 1 wide character |
NOTE: The sizes of variables might be different from those shown in the above table, depending on the compiler and the computer you are using.
typedef Declarations:
You can create a new name for an existing type using typedef. Following is the simple syntax to define a new type using typedef:
typedef type newname;
For example, the following tells the compiler that feet is another name for int:
typedef int feet;
Now, the following declaration is perfectly legal and creates an integer variable called distance:
feet distance;
Enumerated Types:
An enumerated type declares an optional type name and a set of zero or more identifiers that can be used as values of the type. Each enumerator is a constant whose type is the enumeration.
To create an enumeration requires the use of the keyword enum. The general form of an enumeration type is:
enum enum-name { list of names } var-list;
Here, the enum-name is the enumeration’s type name. The list of names is comma separated.
For example, the following code defines an enumeration of colors called colors and the variable c of type color. Finally, c is assigned the value “blue”.
enum color { red, green, blue } c; c = blue;
By default, the value of the first name is 0, the second name has the value 1, the third has the value 2, and so on. But you can give a name a specific value by adding an initializer. For example, in the following enumeration, green will have the value 5.
enum color { red, green=5, blue };
Here, blue will have a value of 6 because each name will be one greater than the one that precedes it.
I would strongly recommend using the new (since C++11) method of defining type aliases:
using newtype = oldtype;
instead of typedefs
typedef oldtype newtype;
The problem I have with typedefs is that after more than 20 years of C++ programming, I still have to stop and think “which one is the new type”. The new syntax is much clearer in that respect.