内含C++经典代码，根据半径计算圆的周长和面积、十和十六进制数混合运算并输出、计算和打印打印乘法九九表等诸多代码，有较为详细的注释。-Containing C++ classic code, according to the radius of the circumference of a circle and area calculations, ten and hexadecimal numbers mixed calculates and outputs, calculate and pr