Data types

Data‒types

• Definition: Data types are used to define the type of data for particular variable. These are specified using specific keyword.

There are three types of data types ‒

1. Fundamental or Primitive or Basic Data types

2. Derived Data types

3. User defined Data types

Data type

• Primitive

• Derived

• User‒defined

1.Basic Data Types

The built‒in data types supported by C++ are enlisted in the following table.

2. Derived Data Types

• These are the data types that are derived or created from the fundamental data types.

• In C++ arrays and strings are considered as derived data types.

Syntax of Arrays

Data_type array_name[size];

Example of Arrays

int a[10];

Syntax of Strings

char array_name[size];

Example of strings

char msg[]=('h','e','l','l','o'};

3. User‒Defined Data Types

• User defined data types are the data types that allow to store multiple values either of same data type or different data type or both.

• In C++ user defined data types are denoted using struct, union or enum.

Enum

• To create user defined type names the keyword enum is used. The syntax of using enum is

enum name{list of names) variables;

For example:

enum day{Monday,Tuesday,Wednesday} d;

d=Tuesday;

• By default the value of first name is 0, second name has value 1 and so on. But we can give some other specific value to the list element. For example

enum day{Monday=10,Tuesday=20,Wednesday=30};

• Following is a simple C++ program that illustrates the use of enum

/***********************************

Program for using enum

**********************************/

#include<iostream>

using namespace std;

int main()

{

       enum mylist{small,middle=5,large} a,b;

        a=middle;

       b=large;

       cout<<"a= "<<a<" b= "<<b;

       return 0;

}

Output

a= 5 b=6

Struct

•  Structure in C is a programming construct that keeps together the variables that need to be in one entity.

•  Structure is a basically the collection of the data members that belong to different data types.

• The keyword struct is used to define the structure in C.

(1) Syntax of C Structure

struct name_of_structure

{

data type member₁;

data type member₂;

data type member₃;

...

data type member_n

};

(2) Example of Structure

struct student

{

       int rollNo;

       char name[20];

       float percentage;

}:

 (3) Accessing Structure Members

We can access the structure member using the dot operator. For example

struct student

{

       int rollNo;

       char name[20];

       float percentage;

}s1,s2;

s1.rollNo=10;

strcpy(s1.name, "AAA");

Here s1 and s2 are the variables of structure using which we can access the members of structure with the help of dot operator.

Example 1: An unsigned int can be twice as large as the signed int. Explain how?

Solution :

1) The sign needs one bit, and the rest are used for the integer.

2) Unsigned uses this bit also as part of the integer. And as one extra bit available is equivalent to doubling the capacity.

3) For instance: Let us assume that the machine is 32 bit wide. For a signed integer, when 32 bits are allocated, 1 bit has to be used for storing the sign information. So the actual number can only be 31 bit wide.

For an unsigned integer, the whole 32 bits can be used.

So the range of signed int will be ‒ 32768 to 32768 and the range of unsigned int will be 0 to 65,535.

Review Questions

1. Describe data types in C++ in detail.

2. What is user defined data types? What is the scope and life time of variable ? Explain using C++ program.     

3. Describe the concept of enumerated data Type in C++ with a proper example.