题目：学生成绩管理是学校教务管理的重要组成部分，其处理信息量很大，本实验是对学生的成绩管理作一个简单的模拟，用菜单选择操作方式完成下列功能：
（1）学生成绩；
（2）查询学生成绩；
（3）插入学生成绩；
（4）删除学生成绩。

我的程序：（能运行，但是功能不全，希望高手指点！）

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <string.h>
#define ERROR 0
#define OK 1
typedef struct Node
{
int id,score;
char name[21];
struct Node *next;
}students,*Linklist;

Linklist creat_new(){  //建立单链表
   Linklist L=NULL;
   students *s;
   int id,score;
   char name[21];
   int flag=0;
   printf("Please input the ID:\n",id);
     scanf("%d",&id);
   while (id!=flag)
   {
     s=new students;
     s->id=id;
     printf("Please input the NAME:\n",name);
     scanf("%s",&name);
     strcpy(s->name,name);
     printf("Please input the SCORE:\n",score);
     scanf("%d",&score);
     printf("Please input the ID（Enter 0 to end):\n",id);
     scanf("%d",&id);
     s->score=score;
     s->next=L;
     L=s;
   }
   return L;
}

students *Get_Linklist(Linklist L,int id){   //以序号查找
   students *s;
   int j=1;
   s=L;
   while(s->next!=NULL&&j<=id)
   { s=s->next;
     j++;
   }
   if(j==id)
    return s;
   else
    return NULL;
}

int Insert_Linklist(Linklist L,int pos,int id,char name[],int score){
  students *p,*s;
    p=Get_Linklist(L,pos-1);
    if(p==NULL)
    { printf("The position was wrong!\n");
      return ERROR;
    }
  else
    { s=new students;
      s->id=id;
      strcpy(s->name,name);
      s->score=score;
      s->next=p->next;
      p->next=s;
      return OK;
    }
}

int Del_Linklist (Linklist L,int pos){ //删除数据
  students *p,*s;
  p=Get_Linklist(L,pos-1);
  if(p==NULL)
   { printf("The position don't exit!\n");
     return ERROR;
   }
  else
    if(p->next==NULL)
    { printf("The position don't exit!\n");
      return ERROR;
    }
  else
    { s=p->next;
      p->next=s->next;
      delete s;
      return OK;
    }
}

main()
{
    int t=1;
    int pos,i;
    Linklist L;
    students *s;
    int id,score;
    char chocie,name[21];
    while(t)
    { printf("\n");
      printf("**********************************\n");
      printf("*  Welcome to the manage system! *\n");
      printf("*         Creat--------1         *\n");
      printf("*         Find---------2         *\n");
      printf("*         Insert-------3         *\n");
      printf("*         Delete-------4         *\n");
      printf("*         Quit---------5         *\n");
      printf("**********************************\n");
      printf("Please enter your chocie:\n");
      chocie=getchar();
       if(chocie=='1')creat_new();
           else
               if(chocie=='2')
                 { printf("Please input the ID:\n");
                   scanf("%d",&i);
                   if(i==s->id)
                     { Get_Linklist(L,i);
                       printf("%d %-5s %-5d\n",s->id,s->name,s->score) ; }
                   else printf("ERROR!\n");
                 }
           else
               if(chocie=='3')
               { printf("Please input the POSITION:\n");
                 scanf("%d",&pos);
                 printf("Please input the ID:\n");
                 scanf("%d",&id);
                 printf("Please input the NAME:\n");
                 scanf("%s",name);
                 printf("Please input the SCORE:\n");
                 scanf("%d",&score);
                 Insert_Linklist(L,pos,id,name,score);
               }
           else
               if(chocie=='4')
               {   printf("Please input the ID:\n");
                   scanf("%d",&pos);
                   if(pos==s->id)
                      Del_Linklist(L,pos);
                   else printf("ERROR!\n");
               }
           else
               if(chocie=='5')
               {
                 t=0;
               }
      }
}