向各位大侠请教了，我的程序是这样的：
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>

#define MAXWORD 100
#define BUFSIZE 1000
#define NDISTINCT 1000

int getch(void);
void ungetch(int c);
int comment(void);
int getword(char *word, int lim);
struct tnode *talloc(void);
char *strdup(char *s);
struct tnode *addtree(struct tnode *p, char *w);
void treestore(struct tnode *p);
void sortlist();

struct tnode *list[NDISTINCT];
int ntn = 0;

char buf[BUFSIZE];   
int bufp = 0;         

struct tnode {              
    char *word;               
    int count;               
    struct tnode *left;      
    struct tnode *right;      
};

main()
{
    struct tnode *root;
    char word[MAXWORD];
    int i;

    root = NULL;
    while (getword(word, MAXWORD) != EOF)
        if (isalpha(word[0]))
            root = addtree(root, word);
    treestore(root);
    sortlist();
    for (i=0; i<ntn; i++)
        printf("%2d:%20s\n",list[i]->count, list[i]->word);
    return 0;
}
       

int getch(void)
{
    if (bufp > 0)
        return buf[--bufp];
    else
        return getchar();
}

void ungetch(int c)
{
    if (bufp >= BUFSIZE)
        printf("ungetch: too many characters\n");
    else
        buf[bufp++] = c;
}

int comment(void)
{
    int c;
    while ((c = getch()) != EOF)
        if (c == '*')
            if ((c = getch()) == '/')
                break;
            else
                ungetch(c);
    return c;
}

int getword(char *word, int lim)
{
    int c;
    char *w = word;

    while (isspace(c = getch()))
        ;
    if (c != EOF)
        *w++ = c;
    if (!isalpha(c)) {
        *w = '\0';
        return c;
    }
    for ( ; --lim > 0; w++)
        if (!isalnum(*w = getch())) {
            ungetch(*w);
            break;
        }
    *w = '\0';
    return word[0];
}

struct tnode *talloc(void)
{
    return (struct tnode *) malloc(sizeof(struct tnode));
}

char *strdup(char *s)
{
    char *p;

    p = (char *) malloc(strlen(s)+1);
    if (p != NULL)
        strcpy(p, s);
    return p;
}

struct tnode *addtree(struct tnode *p, char *w)
{
    int cond;

    if (p == NULL) {
        p = talloc();
        p->word = strdup(w);
        p->count = 1;
        p->left = p->right = NULL;
    } else if ((cond = strcmp(w, p->word)) == 0)
        p->count++;
    else if (cond < 0)
        p->left = addtree(p->left, w);
    else
        p->right = addtree(p->right, w);
    return p;
}

void treesorte(struct tnode *p)
{
    if (p != NULL) {
        treesorte(p->left);
        printf("%4d %s\n", p->count, p->word);
        treesorte(p->right);
    }
}

void sortlist()
{
    int gap, i, j;
    struct tnode *temp;

    for (gap = ntn/2; gap > 0; gap /= 2)
        for (i=gap; i<ntn; i++)
            for (j=i-gap; j>=0; j-=gap) {
                if ((list[j]->count) >= (list[j+gap]->count))
                    break;
                temp = list[j+gap];
                list[j] = list[j+gap];
                list[j+gap] = temp;
            }
}
目的在于想根据单词的出现频率按降序打印输入的各个不同单词，并在每个单词的前面标上它的出现次数。
可vc编译器总是出现：
error LNK2001: unresolved external symbol "void __cdecl treestore(struct tnode *)" (?treestore@@YAXPAUtnode@@@Z)与
fatal error LNK1120: 1 unresolved externals
上网找了其他资料，但并不能解决，现在莱鸟想向高手请教了！

那请问怎么弄？？

我顶！

有啊！怎么会没有？
int getch(void);
void ungetch(int c);
int comment(void);
int getword(char *word, int lim);
struct tnode *talloc(void);
char *strdup(char *s);
struct tnode *addtree(struct tnode *p, char *w);
void treestore(struct tnode *p);
void sortlist();

谢谢！我对    struct tnode *root;进行定义了！不过，我很奇怪？我第一次遇到函数是要定义的；为什么要定义呢？其它函数怎么不用啊？