DATA-TYPES & THEIR USAGE

C++ Data Types

Data types are means to identify the type of data and associated operations of handling it. There are three types of data types:

1. Pre-defined DataTypes
2. Derived Data Types
3. User-defined DataTypes

 Pre-defined DataTypes:

These data types are built-in or predefined data types and can be used directly by the user to declare variables. example: int, char , float, bool etc. Primitive data types available in C++ are:

1.      Integer

2.      Character

3.      Boolean

4.      Floating Point

5.      Double Floating Point

6.      Valueless or Void

7.      Wide Character

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:

1.      Function

2.      Array

3.      Pointer

4.      Reference

Abstract or User-Defined Data Types:

 These data types are defined by user itself. Like, defining a class in C++ or a structure. C++ provides the following user-defined datatypes:

1.      Class

2.      Structure

3.      Union

4.      Enumeration

5.      Typedef defined DataType

In this article, the Pre-defined DataType is explained:

There are five data types in the C subset: character, integer, floating-point,

double floating-point, and valueless (char, int, float, double, and void, respectively).

To the five basic data types defined by C, C++ adds two more: bool and wchar_t.

The exact format of floating-point values will depend upon how they are implemented.

Integers will generally correspond to the natural size of a word on the host computer.

Values of type char are generally used to hold values defined by the ASCII character

set. Values outside that range may be handled differently by different compilers.

The range of float and double will depend upon the method used to represent

the floating-point numbers. Whatever the method, the range is quite large.

The typical sizes are mentioned below

Or you can run this code:

#include<iostream>

using namespace std;

 

int main()

{

    cout << "Size of char : " << sizeof(char) 

      << " byte" << endl;

    cout << "Size of int : " << sizeof(int)

      << " bytes" << endl;

    cout << "Size of short int : " << sizeof(short int) 

      << " bytes" << endl;

    cout << "Size of long int : " << sizeof(long int) 

       << " bytes" << endl;

    cout << "Size of signed long int : " << sizeof(signed long int)

       << " bytes" << endl;

    cout << "Size of unsigned long int : " << sizeof(unsigned   long int) 

       << " bytes" << endl;

    cout << "Size of float : " << sizeof(float) 

       << " bytes" <<endl;

    cout << "Size of double : " << sizeof(double) 

       << " bytes" << endl;

    cout << "Size of wchar_t : " << sizeof(wchar_t) 

       << " bytes" <<endl;

     

   

}

Like this

Then you will see an output like this

DataTypes and their forms

1.   Integer: Keyword used for integer data types is int.

2.   Character: Character data type is used for storing characters. Keyword used for character data type is char.

3.   Boolean: Boolean data type is used for storing boolean or logical values. A boolean variable can store either true or false. Keyword used for boolean data type is bool.

4.   Floating Point: Floating Point data type is used for storing single precision floating point values or decimal values. Keyword used for floating point data type is float.

5.   Double Floating Point: Double Floating Point data type is used for storing double precision floating point values or decimal values. Keyword used for double floating point data type is double..

6.   void: Void means without any value. void datatype represents a valueless entity. Void data type is used for those function which does not returns a value.

7.   Wide Character: Wide character data type is also a character data type Represented by wchar_t.

Modifying the Basic Types

Except for type void, the basic data types may have various modifiers preceding them.

You use a modifier to alter the meaning of the base type to fit various situations more

precisely. The list of modifiers is shown here:

signed

unsigned

long

short

You can apply the modifiers signed, short, long, and unsigned to integer base types.

You can apply unsigned and signed to characters. You may also apply long to double.

The use of signed on integers is allowed, but redundant because the default integer

declaration assumes a signed number. The most important use of signed is to modify

char in implementations in which char is unsigned by default.

The difference between signed and unsigned integers is in the way that the high order

bit of the integer is interpreted. If you specify a signed integer, the compiler

generates code that assumes that the high-order bit of an integer is to be used as a

sign flag. If the sign flag is 0, the number is positive; if it is 1, the number is negative.

In general, negative numbers are represented using the two's complement approach,

which reverses all bits in the number (except the sign flag), adds 1 to this number, and

sets the sign flag to 1.

Signed integers are important for a great many algorithms, but they only have half

the absolute magnitude of their unsigned relatives. For example, here is 32,767:

0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

If the high-order bit were set to 1, the number would be interpreted as −1. However,

if you declare this to be an unsigned int, the number becomes 65,535 when the high order

bit is set to 1.

See here 

check the values at that website mentioned above :

-32767                                               1000000000000001                                   

-65535                                               10000000000000001

 32767                                               0111111111111111

 65535                                               01111111111111111

Hope that helps, its two’s compliment method for binary conversion

Declaration of variables

C++ is a strongly-typed language, and requires every variable to be declared with its type before its first use. This informs the compiler the size to reserve in memory for the variable and how to interpret its value.: we simply write the type followed by the variable name . For example:

1.      int a;

2.      float mynum;

The first one declares a variable of type int with the identifier a. The second one declares a variable of type float with the identifier mynum. Once declared, the variables a and mynum can be used within the rest of their scope in the program.

If declaring more than one variable of the same type, they can all be declared in a single statement by separating their identifiers with commas. For example:

int a, b ;

This declares three variables (a, b), all of them of type int, and has exactly the same meaning as:

1             int a;

2             int b;

if you run this code

String Constants

C/C++ supports one other type of constant: the string. A string is a set of characters

enclosed in double quotes. For example, "this is Science Geek" is a string.

. Although C allows you to define string constants, it does not formally have a string data type.

(C++ does define a string class, however.)

You must not confuse strings with characters. A single character constant is enclosed in single quotes, as in 'a'. However, "a" is a string containing only one letter. in single quotes, as in 'a'. However, "a" is a string containing only one letter     

if you run this the result will be like this

Backslash Character Constants

Enclosing character constants in single quotes works for most printing characters. A

few, however, such as the carriage return, are impossible to enter into a string from the

keyboard. For this reason, C/C++ include the special backslash character constants shown  

    

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