有五个学生，每个学生有3门课的成绩，从键盘输入以上数据（包括学生号，姓名，三门课成绩），计算出平均成绩，况原有的数据和计算出的平均分数存放在磁盘文件"stud"中。-There are five students, each student has 3 class results, more than from the keyboard input data (including student number, name, three-course results), calculate the average grade, status of the original data and calculated the average score placed In the disk file " stud"　in.