A nested loop is a loop placed inside the body of another loop. The inner loop executes completely for each iteration of the outer loop.

Nested loops are commonly used when working with two-dimensional data, generating tables, processing matrices, and performing repeated operations across multiple dimensions.

Source Code #

#include <iostream>

int main()
{
    for (int row = 1; row <= 3; ++row)
    {
        for (int column = 1; column <= 4; ++column)
        {
            std::cout << row << "," << column << "  ";
        }

        std::cout << '\n';
    }

    return 0;
}

Output #

1,1  1,2  1,3  1,4
2,1  2,2  2,3  2,4
3,1  3,2  3,3  3,4

Explanation #

• The outer for loop controls the value of row.
• The inner for loop controls the value of column.
• For every iteration of the outer loop, the inner loop executes all of its iterations.
• When row is 1, the inner loop runs with column values from 1 through 4.
• The outer loop then increments row to 2, and the inner loop starts again from column = 1.
• This process continues until the outer loop condition becomes false.
• The inner loop is completely executed before the outer loop proceeds to its next iteration.
• Nested loops can contain other loop types, such as while or do-while loops.
• return 0; terminates the program successfully.