Data Types

• Data type is defining an attribute to the variable.
• It defines the set of legal data the variable can store. The basic data types are int, char, and float.
• Integer, the data type ‘int’ are whole numbers with a range of values supported by a particular machine. For instance, in a 16 bit word length machine, the integer values lie between -32768 to 32767.
• ‘C++’ facilitates some control over the integer data type by providing sub data types namely short int, int, long int.
• Short int represents fairly small integer values and requires half the amount of storage as a normal int uses.
• Similarly a long int represents fairly higher integer values and requires generally twice the number of bits as a normal int uses. Nevertheless these are highly machine dependent
• Another option in integer data type is declaring it as unsigned. This unsigned integer uses all bits for the magnitude of the number and is always positive. For instance, in a 16 bit machine the range of unsigned integer is 0 to 65,535. Thus long and unsigned are intended for increasing the range of values.
• Floating point type: Floating point numbers are numbers that have a decimal point. This data type in ‘C++’ is an attribute for real numbers.
  
• The corresponding declaration is, float a;
• which instructs the compiler that the variable ‘a’ belongs to the data type real. If you want to initialize the variable, then
• float a;
• a = 14.752;
• This can also be achieved through a single statement. float a = 14.752;
• The keyword float defines the floating point number.
• When more accuracy is required, another sub data type, double under the float data type can be used.
• Obviously this double data type uses twice the storage as that of the float data type (8 bytes).
• To display a double value the format specifier %f is used to obtain the standard floating point notation and %e for scientific or exponential notation
• Character data type: The char keyword defines a character data type. Thus the declaration for this is char x;
• x = ‘a’;
• The variable x is of type character and is initialized to the character ‘a’. The same effect could be achieved as,
• char x = ‘a’;

Declarations

• The modern programming languages clearly separate the data and the control statements.
• All the data is declared first. This makes the program more readable and also provides the information to the compilers to allocate memory spaces.
• The data and control are well separated by making the former to precede textually, in the name of declarations. Such declarations follow the syntax,
• type identifier v1, v2......vn; Example: int n1, n2, n3; Example: float x, y, z;
• Initialization of the data is also possible at the time of declaration. Example: int x =72;
• Data declaration does two significant tasks for each variable. They are:

1. Tells the compiler what the variable name is.
2. Specifies what type of data the variable will hold.

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