Error in struct definition of Student & List

Question

I've tried to define structures of listNode, List and student and I get the error message:

Error   1   error LNK2019: unresolved external symbol _WinMain@16 referenced in       function ___tmainCRTStartup   C:\Users\Samsung\Documents\Visual Studio 2013\Projects\ICS Ex 03\ICS Ex 03\MSVCRTD.lib(crtexew.obj) ICS Ex 03 
Error   2   error LNK1120: 1 unresolved externals   C:\Users\Samsung\Documents\Visual Studio 2013\Projects\ICS Ex 03\Debug\ICS Ex 03.exe    ICS Ex 03

Here is the code:

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <malloc.h>
#include <math.h>

typedef struct list_node
{
    char*  dataPtr;
    struct list_node*  next;
}ListNode;

typedef struct list
{
    ListNode* head;
    ListNode* tail;
}List;

typedef struct  student
{
    List first;
    int grade;
} Student;




Student unScramble(List  lst);
List makeEmptyList(List* lst);
void insertDataToEndList(List *lst, char ch);
void printStudent(Student *student);
void freeList(List* lst);
int isEmptyList(List* lst);

void main()
{
    List lst;
    Student student;
    char ch;
    makeEmptyList(&lst);
    printf("Please enter the scrambled student:\n");
    ch = (char)getchar();
    while (ch != '\n')
    {
        insertDataToEndList(&lst, ch);
        ch = (char)getchar();
    }
    student = unScramble(lst);
    printStudent(&student);
    freeList(&student.first);
}
Student unScramble(List  lst)
{
    int num, count = 0;
    Student stu;
    stu.first = makeEmptyList(&stu.first);
    stu.grade = 0;
    if (*lst.tail->dataPtr >= '0' && *lst.tail->dataPtr <= '9')
    {
        num = (int)lst.tail->dataPtr - '0';
        stu.grade += (num*((int)pow(10, count)));
        count++;
    }
    /*if (lst.tail->dataPtr >= 'a' && lst.tail->dataPtr <= 'z')*/
    return stu;

}
List makeEmptyList(List* lst)
{
    lst->head = lst->tail = NULL;
    return *lst;
}
void insertDataToEndList(List *lst, char ch)
{
    ListNode *newHead;
    newHead = malloc(sizeof(ListNode));
    newHead->dataPtr = &ch;
    newHead->next = lst->head;
    if (lst->tail == NULL)
        lst->tail = newHead;
    lst->head = newHead;
}
void printStudent(Student *student)
{
    printf("Name: %s", student->first);
    printf("\n");
    printf("Grade: %s", student->grade);
}
void freeList(List *lst)
{
    ListNode *p, *q;

    if (isEmptyList(lst))
        return;

    p = lst->head;

    while (p->next != NULL)
    {
        q = p;
        p = p->next;
        free(q);
    }
    free(p);
}
int isEmptyList(List *lst)
{
    return (lst->head == NULL);
}

What went wrong?