need help with this program (student information manager with linkedlist)

[omidelf]

this code stores information about students (with linked list) , i need to add these abilities to it :

1.add and remove course name and get the grade of the course
2.calculating the GPA of students based on their grades
3.search for a specific student

#include <stdio.h>
#include <stdlib.h>

#define TRUE 1
#define FALSE 0


struct node {                                                               /* node structure definition */
   int id;
   char name[20];
   float gpa;
   struct node *next;
};

typedef struct node * nodeptr;                                  /* data type for node ptrs */

nodeptr addnode(nodeptr list);                                /* allocate memory for new node */
nodeptr insert(nodeptr list, nodeptr p);                   /* insert a node */
int deletenode(nodeptr *,int);                                   /* locate & delete a node */
void printlist(nodeptr);                                               /* print list contents */

int main(void)
{

   nodeptr list = NULL;                                               /* pointer to list */
   int del;                                                                      /* student to be deleted from list */
   int sel;                                                                      /* menu selection */

   while(true)
   {
                        printf("\nMenu:\n");
                        printf("1 - Add a Student\n");
                        printf("2 - Delete a Student\n");
                        printf("3 - Print Students\n");
                        printf("4 - Exit\n");
                        printf("Make your selection ->");
                        fflush(stdin);
                        scanf("%d", &sel);
                        printf("\n");
                        switch(sel)
                        {
                                    case 1:
                                                list=addnode(list);
                                                break;

                                    case 2:
                                                printf("Enter Student ID to delete a student -> ");
                                                scanf("%d",&del);

                                                if (!deletenode(&list,del))      /* try to delete node, return flag */
                                                {
                                                            printf("Student ID %d was not on the list\n", del);
                                                }
                                                else
                                                {
                                                            printf("%d has been deleted\n",del);
                                                }
                                                break;

                                    case 3:
                                                printlist(list);
                                                break;

                                    case 4:
                                                printf("Bye!\n");
                                                exit(1);

                                    default:
                                                printf ("Invalid selection.  Please try again.\n\n\n");
                                                break;
                        }
   }
   return 0;
}


nodeptr addnode(nodeptr list)
{
   /* This function allocates memory for new node*/
   nodeptr p;

   if ((p = (nodeptr)malloc(sizeof(struct node))) != NULL)
            {
             p->next = NULL;                   /* initialize next to NULL */
             printf("Please enter student ID: ");
             fflush(stdin);
             scanf("%d", &p->id);
             printf("Please enter student name: ");
             fflush(stdin);
             gets(p->name);
             printf("Please enter student GPA: ");
             fflush(stdin);
             scanf("%f", &p->gpa);

             list = insert(list,p);                                         /* save p into list */
    }
    else
            {                                                                       /* else insufficient memory */
             printf("Insufficient memory to build entire list.\n");
            }
            return(list);
}

nodeptr insert(nodeptr list, nodeptr p)
{

   nodeptr q;

   if ((list == NULL) || (list->id >= p->id)) {                 /* does p go first? */
      p->next = list;                                                        /* put p on front */
      list = p;
   } else {                                                                                  /* else search for spot */
      q = list;                                                                              /* use q to locate spot */
      while ((q->next != NULL) && (q->next->id < p->id))
             q = q->next;
      p->next = q->next;                                                           /* attach back of list to p */
      q->next = p;                                                          /* attach front of list to p */
   }
   return(list);
}

int deletenode(nodeptr *list,int target)
{
  

   nodeptr p,q;                                                            /* p - target, q - predecessor */
   int found = FALSE;                                                /* flag if target found */

   if ((*list)->id == target)
   {                                                                                /* if target is at head of list */
      p = *list;                                                                /* p points to target node */
      *list = (*list)->next;                                               /* update external pointer */
      found = TRUE;                                                     /* set flag - target found */
   }
   else
   {                                                                                /* else use loop to search list */
      q = *list;
      while ((q->next != NULL) && (q->next->id < target))
              {
                          q = q->next;                                      /* stop if found or target not there*/
              }
      if (q->next != NULL)
              {                                                                     /* will be true if target not on list*/
         if (q->next->id == target)
                         {                                                          /* is this the target? */
                                    found = TRUE;                       /* set flag - target found */
                                    p = q->next;                            /* p points to target node */
                                    q->next = p->next;                 /* reattach remainder of list to q */
         }
      }
   }
   if (found)
      free(p);                                                                  /* free memory space if necessary */
   return(found);                                                          /* return flag to main */
}


void printlist(nodeptr list)
{
   /* Print all info about all students */
   while (list != NULL) {
      printf("ID: %d \n",list->id);
              printf("Name: %s \n",list->name);
              printf("GPA: %f \n\n",list->gpa);
      list = list->next;
   }
}