diff --git a/task4.cpp b/task4.cpp
new file mode 100644
index 0000000..f139721
--- /dev/null
+++ b/task4.cpp
@@ -0,0 +1,120 @@
+#include <stdio.h>
+//定义结构体
+struct Student
+{
+	int ID;//学号 
+	int classes;
+	float math_grade;
+	float physics_grade;
+	float English_grade;
+	float sum;
+};
+
+int main()
+{
+	struct Student information[4];
+	//已有三个同学的信息
+	information[0].ID=10001;information[0].classes=11;
+	information[0].math_grade=99.5;
+	information[0].physics_grade=88.5;
+	information[0].English_grade=89.5;
+	
+	information[1].ID=10002;information[1].classes=12;
+	information[1].math_grade=77.9;
+	information[1].physics_grade=56.5;
+	information[1].English_grade=87.5;
+	
+	information[2].ID=10003;information[2].classes=11;
+	information[2].math_grade=92.5;
+	information[2].physics_grade=99.0;
+	information[2].English_grade=60.5;
+	
+	//输入新同学 
+	scanf("%d%d%f%f%f",&information[3].ID,\
+	&information[3].classes,&information[3].math_grade,\
+	&information[3].physics_grade,&information[3].English_grade); 
+	struct Student newstudent=information[3];
+	//判断是否已在系统里
+	if(newstudent.ID==information[0].ID||\
+	newstudent.ID==information[1].ID||\
+	newstudent.ID==information[2].ID)//新同学已在系统里 
+	{
+		for(int i=0;i<=2;i++)
+		{
+			if(newstudent.ID==information[i].ID)
+			{
+				printf("%d %d %.1f %.1f %.1f \n",\
+				information[i].ID,information[i].classes,\
+				information[i].math_grade,information[i].physics_grade,\
+				information[i].English_grade);
+			}
+		}		
+	}
+	else//新同学不在系统里 
+	{
+		//排序:班级从小到大【顺便把每个人的成绩记录】 
+		for(int i=0;i<=3;i++)
+		{
+			for(int j=0;j<=2;j++)
+			{
+				if(information[j].classes>information[j+1].classes)
+				{
+					struct Student tmp=information[j];
+					information[j]=information[j+1];
+					information[j+1]=tmp;
+				}
+			}
+			information[i].sum=+information[i].math_grade+\
+			information[i].physics_grade+information[i].English_grade;
+		 } 
+		 
+		 //排序 ：对同一班级排序
+		 for(int i=0;i<=3;i++)
+		 {
+		 	int con=0;//记录连续了几人 
+		 	for(int j=1;j<=3-i;j++)
+		 	{
+		 		if(information[i].classes==information[i+j].classes)
+		 		{con++;
+				 }
+				 else
+				 {
+				 break;
+				 }
+			 }
+			 
+			 if(con)//有人是同班同学，在此内排序 
+			 {
+			 	for(int m=i;m<i+con;m++)
+			 	{
+			 		for(int n=i;n<=i+con-1;n++)
+			 		{
+			 			if(information[n].sum<information[n+1].sum)
+				 		{
+				 			struct Student tmp=information[n];
+							information[n]=information[n+1];
+							information[n+1]=tmp;
+						 }
+					 }
+				 }
+			 }
+			 
+			 i=i+con;
+		  } 
+	
+		for(int i=0;i<=3;i++)
+		{
+			printf("%d %d %.1f %.1f %.1f ",information[i].ID,\
+			information[i].classes,information[i].math_grade,\
+			information[i].physics_grade,information[i].English_grade);
+			if(newstudent.ID==information[i].ID)
+			{
+				printf("inserted");
+			}
+			printf("\n");
+		
+		}
+	}
+}
+
+