Added comments.

GCD_of_n_numbers.cpp

@@ -1,3 +1,4 @@
+//This program aims at calculating the GCD of n numbers by division method
 #include <iostream>
 using namepsace std;
 int main()
@@ -6,16 +7,17 @@ int main()
   cin >> n;
   int a[n];
   int i,j,gcd;
+  cout << "Enter the n numbers:" << endl;
   for(i=0;i<n;i++)
     cin >> a[i];
-  j=1;
+  j=1; //to access all elements of the array starting from 1
   gcd=a[0];
   while(j<n)
   {
-    if(a[j]%gcd==0)
-     j++;
+    if(a[j]%gcd==0) //value of gcd is as needed so far
+     j++;          //so we check for next element
     else
-     gcd=a[j]%gcd;
+     gcd=a[j]%gcd; //calculating GCD by division method
   }
   cout << "GCD of entered n numbers:" << gcd;
 }