编程计算图形的面积。程序可计算圆形、长方形、正方形的面积，运行时先提示用户选择图形的类型，然后，对圆形要求用户输入半径值，对长方形要求用户输入长和宽的值，对正方形要求用户输入边长的值，计算出面积的值后将其显示出来。-Calculate the area of graphics programming. Program calculates circular, rectangular, square area, run-time prompts the user to first select the type of graph, and then require the user to enter the circular radius of a rectangular require the user to input the length and width of the value, require the user to input side of the square long value, calculate the value of the area after the show.