In c++ we use variables to store the value of a number. The type of the value is needed to be declared first because according to that it will allocate the memory to particular variable.
Every variable is assigned with the unique memory address.
There are two types of variables:-

• Local variable
• Global variable

#include 
using namespace local;

int main ()
{
  // Declaration of local variable:
  int x, y;
  int z;

  // actual initialization
  x = 5;
  y = 10;
  z = x * y;

  cout << z;

  return 0;
}

GLOBAL VARIABLES:-Global variables are declared on the top of the program or we can say outside the function. We can use that variable throughout the program.
e.g of global variable:

#include 
using namespace global;

// Declaration of global variable :
int m;

int main ()
{
  // Declaration of local variable:
  int x, y;

  // actual initialization
  x = 5;
  y = 10;
  m = x * y;

  cout << m;

  return 0;
}