Datatypes and Variables

variables

• Variables: Variables are used to store data in a programming language.

Data Types

Data types determine the kind of data that can be stored in a variable.

Integer : Used for whole numbers, e.g., 1, 2, 3, 4. In C/C++, it is represented as int.

Floating-Point: Used for numbers with a decimal point, e.g., 7.2, 8.4, 3.5, 4.3. In C/C++, it is represented as float.

Character: Used for single characters, e.g., 'a', 'z', 'v', 'b'. In C/C++, it is represented as char.

Boolean: Used for Storing logical values, e.g., true or false. In C/C++ it is represented as bool.

How to define variable

To define a variable, you specify its data type followed by the variable name.

<datatype> <variable_name>;
int          age;

<char> <variable_name>;
char          gender;

<float> <variable_name>;
float          weight;

<bool> <variable_name>;
bool          flag;

Declaring and Assigning Values

#include <iostream>
using namespace std;

int main() {
    int age; // Declaration
    age = 22; // Assigning a value
    cout << age;
    return 0;
}

Output :

22

Explanation :

Line 4 : declare variable age
Line 5 : assign value 22 in age variable.
Line 5 : print vairble age using cout object.

Addition of Two Number :

#include <iostream>
using namespace std;

int main() {
    int val1 = 10; // Declaration and assignment
    int val2 = 20; // Declaration and assignment
    int sum = val1 + val2;
    cout << sum;
    return 0;
}

⚙️ Output :

30

Explanation :

Line 4 : declare variable val1 and assign value 10.
Line 5 : declare variable val2 and assign value 20.
Line 6 : declare sum variable and assign the addition of val1 + val2 .
Line 7 : print sum variable by using cout object.

Rules to declared Variable

1. A variable name must start with a letter a-z or A-Z or the underscore _ character.
2. A variable name cannot start with a number.
3. Variable names are case-sensitive, which means name and Name are considered different variables.
4. A variable name can not used reserved keyword
5. A variable name can include a-z,A-z, 0-9, and _

Example 1 :

#include <iostream>
using namespace std;

int main() {

    int age = 20;

    cout<<"Age =";

    cout<<age;

    return 0;
}

Output :

Age = 20

Explanation :

Line 5 : declare age variable assign value to the age variable is 20.
LIne 7 : print the "Age = " string.
Line 9 : print age variable using cout object.

Example 2 :

#include <iostream>
using namespace std;

int main() {

    int age = 22;

    cout<<"My age is "<<age;

    return 0;
}

Output :

my age is 22

Line 5 : declare age and assign value 22.
Line 7 : print My age is string and age variable using cout object.

Example 3 :

#include <iostream>
using namespace std;

int main() {

    int age = 20;
    int weight = 50;

    cout<<"My age is"<<age<<"& Weight is"<<weight;

    return 0;
}

Output :

My age is 20 & weight is 50

Explanation :

Line 5 : Declare age variable and assign value 20.
Line 6 : Declare weight variable and assign value 50.
Line 7 : print age and weight using cout object.