Variables are used in C++ to store and use the data within a program. In C++, variables are declared as follows:

Syntax:-

datatype variableName = value;

Example:-

#include <iostream> // Include the input/output headers that are required.

int main() {
    // Declare variables
    int a;                   // declaration of the integer variable "a"
    float s;        // declaration of the float variable "s"
    char g;            // The definition of a character variable called "g"
    
                                  // Initialize variables
    a = 25;                // Assign a value to the "a" variable
    s = 5.75;    // Assign a value to the "s" variable
    g= 'A';               // Assign a value to the "g" variable
    
                                   // Print values
    std::cout << "Age: " << a << std::endl;
    std::cout << "S: " << s << std::endl;
    std::cout << "Grade: " << g << std::endl;
    
    return 0;
}

• We include the <iostream> header, which is necessary for using input/output streams like std::cout (output) and std::cin (input).
• Inside the 'main' function, we declare variables using their data types (e.g., 'int', 'double', 'char') followed by their names.
• We use the assignment operator to initialize the stated variables with values.