Data Handling

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C++ supports a large number of data types. The built in or basic data types supported by C++ are integer, floating point and character. These are summarized in table along with description and memory requirement

Type	Byte	Range	Description
int	2	-32768 to +32767	Small whole number
long int	4	-2147483648 to +2147483647	Large whole number
float	4	3.4x10-38 to 3.4x10+38	Small real number
double	8	1.7x10-308 to 1.7x10+308	Large real number
long double	10	3.4x10-4932 to 3.4x10+4932	Very Large real number
char	1	0 to 255	A Single Character

Variables

It is a location in the computer memory which can store data and is given a symbolic name for easy reference. The variables can be used to hold different values at different times during the execution of a program.

To understand more clearly we should study the following statements:
Total = 20.00;
In this statement a value 20.00 has been stored in a memory location Total.

Declaration of a variable

Before a variable is used in a program, we must declare it. This activity enables the compiler to make available the appropriate type of location in the memory.
float Total;

You can declare more than one variable of same type in a single single statement
int x,y;

Initialization of variable

When we declare a variable it's default value is undetermined. We can declare a variable with some initial value.
int a = 20;

 

Input/Output (I/O)

C++ supports input/output statements which can be used to feed new data into the computer or obtain output on an output device such as: VDU, printer etc. The following C++ stream objects can be used for the input/output purpose.

cin console input
cout console output

cout is used in conjuction with << operator, known as insertion or put to operator.
cin is used in conjuction with >> operator, known as extraction or get from operator.

cout << “My first computer";Once the above statement is carried out by the computer, the message "My first computer" will appear on the screen.

cin can be used to input a value entered by the user from the keyboard. However, the get from operator>> is also required to get the typed value from cin and store it in the memory location.
Let us consider the following program segment:
int marks; 
cin >> marks; In the above segment, the user has defined a variable marks of integer type in the first statement and in the second statement he is trying to read a value from the keyboard.

 

Type Conversion

The process in which one pre-defined type of expression is converted into another type is called conversion. There are two types of conversion in C++.

1. Implicit conversion
2. Explicit conversion

Implicit conversion
Data type can be mixed in the expression. For example
double a; 
int b = 5; 
float c = 8.5; 
a = b * c;

When two operands of different type are encountered in the same expression, the lower type variable is converted to the higher type variable. The following table shows the order of data types.

Order of data types
Data type long double double float long int char	order (highest) To (lowest)

The int value of b is converted to type float and stored in a temporary variable before being multiplied by the float variable c. The result is then converted to double so that it can be assigned to the double variable a.

Explicit conversion
It is also called type casting. It temporarily changes a variable data type from its declared data type to a new one. It may be noted here that type casting can only be done on the right hand side the assignment statement.
T_Pay = double (salary) + bonus;
Initially variable salary is defined as float but for the above calculation it is first converted to double data type and then added to the variable bonus.

Constants

A number which does not change its value during execution of a program is known as a constant. Any attempt to change the value of a constant will result in an error message. A constant in C++ can be of any of the basic data types, const qualifier can be used to declare constant as shown below:
const float pi = 3.1415;
The above declaration means that Pi is a constant of float types having a value 3.1415.
Examples of valid constant declarations are:
const int rate = 50;
const float pi = 3.1415;
const char ch = 'A';

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