for – missing sections

As stated before, each of the three for sections can be missing, with the consequence that it simply won’t be executed. In the following loop: 
for(int i = 0; i < 5;)
{
     cout << i << " ";
     i++;
}
the increment section is missing, and the iteration variable is increased within the body. In the next one, the condition section is missing: 
for(int i = 1; ; i++)
{
     cout << i << " ";
     if(!(i%10))
     {
           cout << "Get out of the loop?(y/n) ";
           cin >> c;
           if(c == 'y')
                break;
     }
}
The loop is exited by the break if and when the condition c == 'y' is met. In the following loop, instead: 
char j = 'a';
for(; j < 'f'; j++)
     cout << j << " ";
the initialization section is missing. The loop is based upon a variable declared and initialized outside the loop. Any combination of the three for sections might be absent, combining as a consequence the effects described above. In case all three sections are missing, the loop keeps iterating indefinitely, until it is broken out of, for example by a break statement just like above, or by a goto or a return, or an exit. For example: 
for( ; ; )
{
     cout << "Get out of the loop?(y/n) ";
     cin >> c;
     if(c == 'y')
           break;
}


Example


#include <iostream>
using namespace std;

int main()
{   
     for(int i = 0; i < 5;)
     {
           cout << i << " ";
           i++;
     }
     cout << endl << endl;

     char c;
     for(int i = 1; ; i++)
     {
           cout << i << " ";
           if(!(i%10))
           {
                cout << "Get out of the loop?(y/n) ";
                cin >> c;
                if(c == 'y')
                     break;
           }
     }
     cout << endl << endl;

     char j = 'a';
     for(; j < 'f'; j++)
           cout << j << " ";

     cout << endl << endl;

     for( ; ; )
     {
           cout << "Get out of the loop?(y/n) ";
           cin >> c;
           if(c == 'y')
                break;
     }
}

(Possible) Output

0 1 2 3 4

1 2 3 4 5 6 7 8 9 10 Get out of the loop?(y/n) n
11 12 13 14 15 16 17 18 19 20 Get out of the loop?(y/n) n
21 22 23 24 25 26 27 28 29 30 Get out of the loop?(y/n) n
31 32 33 34 35 36 37 38 39 40 Get out of the loop?(y/n) n
41 42 43 44 45 46 47 48 49 50 Get out of the loop?(y/n) y

 
a b c d e

Get out of the loop?(y/n) n
Get out of the loop?(y/n) n
Get out of the loop?(y/n) n
Get out of the loop?(y/n) y