For structure

The for statement executes the code in the braces for a known number of times. Usually, the for statement is used to iterate over arrays.

General syntax:

for(initial_value_for_a_counter_variable; stop_contidion_for_counter_variable; increment_decrement_counter_variable)
{
    Execute all statements inside the braces
}

Practical example:

In the following example, we store six numbers from lottery in a standard vector and iterate over the vector using a for statement to display the numbers.

#include <iostream>
#include <vector>

int main()
{
    //we have a standard vector of integers in which we want to store the numbers from the lottery.
    std::vector<int> lotteryNumbers;

    //we add the numbers in the vector
    lotteryNumbers.push_back(5);
    lotteryNumbers.push_back(39);
    lotteryNumbers.push_back(10);
    lotteryNumbers.push_back(21);
    lotteryNumbers.push_back(1);
    lotteryNumbers.push_back(40);

    //we use a for statement to show the numbers from the vector.
    std::cout << "The numbers from the lottery are: ";
    for(unsigned int i = 0; i < lotteryNumbers.size(); i++)
    {
        std::cout << lotteryNumbers.at(i) << " ";
    }

    return 0;
}

Note: If the size of the vector would be zero, the for statement would not be executed

Practical examples of using a "for" control statement

In a for statement, any condition can be omitted but it must exist somewhere else in order to have the same behavior.

First example:

#include <iostream>

int main()
{
    int n = 0;

    for(; n < 10; n++)
    {
        //execute statements
    }
}

Second example:

#include <iostream>

int main()
{
    int n = 0;

    for(; n < 10;)
    {
        //execute statements
        n++;
    }
}

Third example:

#include <iostream>

int main()
{
    int n = 0;

    for(;;)
    {
        if(n >= 10)
        {
            break;
        }
        else
        {
            n++;
        }
    }
}

All three examples produce the same output.