怎么给表格外面加边框

最外面的边框是怎么添加的，求解答，不会加那个框，只会拉一条横线在上面变成边框

void drawBoard() // 打印当前表格
{
    cout << "    ╔";
    for (int i = 1; i <= 6; i++)
        cout << "════";
    cout << "═╗\n";
    // 输出中间部分
    for (int i = 1; i <= 12; i++) // 行
    {
        cout << "    ║";
        for (int j = 1; j <= 12; j++) // 列
        {
            cout << num[i][j] << " ";
        }
        cout << " ║" << endl;
    }
    cout << "    ╚";
    for (int i = 1; i <= 6; i++)
        cout << "════";
    cout << "═╝\n";
}

<table border="1">