求大神帮忙告诉我这个程序的 程序及各个模块说明；

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<malloc.h>
#define LEN
sizeof(struct STU)
#define MAX 20
#define OK
0
#define ERROR -1
void Dis_main_meau(void);
void Display(void);
void Insert(void);
int Delete(void);
void Input(void);
/*============构建结构体====================*/
struct STU
{
long
int lNumber;
char
chName[MAX];
int iMath;
int iChinese;
int
iSum;
struct
STU *next;
};
struct STU *g_stHead = NULL;
/*============主界面显示====================*/
void Dis_main_meau(void)
{
printf("\n 欢迎使用学生信息管理系统 \n");
printf("===========================================\n");
printf("* 1:录入
*\n");
printf("* 2:显示
*\n");
printf("* 3:删除
*\n");
printf("* 4:添加
*\n");
printf("* 0:退出
*\n");
printf("===========================================\n");
}

/*===============录入学生成绩==============*/
void Input(void)
{
struct
STU *stNode = NULL;
struct
STU *stTemp = NULL;
int
i=0;
stNode=(struct
STU *)malloc(LEN);
if
(NULL == stNode)
{
exit(-1) ;
}
memset(stNode,
0, sizeof(LEN));
printf("学生学号:");
scanf("%ld",&stNode->lNumber);
printf("学生姓名:");
scanf("%s",stNode->chName);
printf("语文成绩:");
scanf("%d",&stNode->iChinese);
printf("数学成绩:");
scanf("%d",&stNode->iMath);
//当输入两门课成绩同时为0是结束建表
while
((0!=stNode->iChinese)||(0!=stNode->iMath))
{
i+=1;
if (1 == i)
{
g_stHead=stNode;
}
else
{
stTemp->next=stNode;
}
stTemp=stNode;
stNode=(struct STU *)malloc(LEN);
if (NULL == stNode)
{
exit(-1)
;
}
memset(stNode, 0, sizeof(LEN));
printf("学生学号:");
scanf("%ld",&stNode->lNumber);
printf("学生姓名:");
scanf("%s",stNode->chName);
printf("语文成绩:");
scanf("%d",&stNode->iChinese);
printf("数学成绩:");
scanf("%d",&stNode->iMath);
}
stTemp->next=NULL;
return;
}
/*===============显示班级成绩==============*/
void Display(void)
{
struct
STU *stTemp = NULL;
stTemp
= g_stHead;
printf("学生信息如下\n\r");
printf("姓名\t学号\t语文\t数学\n\r");
while
(stTemp)
{
printf("%s\t%ld\t%d\t%d\n\r",
stTemp->chName,stTemp->lNumber,stTemp->iChinese, stTemp->iMath);
stTemp = stTemp->next;
}
return;
}
/*===============学生信息删除==============*/
int Delete(void)
{
char
chStr[MAX] = {0};
printf("学生姓名:");
scanf("%s",
chStr);
if
(NULL == g_stHead)
{
printf("链表为空\n\r");
return ERROR;
}

//只有一个
if
(NULL == g_stHead->next)
{
//只有一个且为所要删除的节点
if (!(strcmp(chStr, g_stHead->chName)))
{
free(g_stHead);
g_stHead
= NULL;
printf("\n删除成功\n\n\r");
return
OK;
}
printf("未找到符合条件的节点\n\r");
return ERROR;
}
struct
STU *stTemp = NULL;
struct
STU *stPre = NULL;
stTemp
= g_stHead;
stPre
= stTemp;
while
((strcmp(chStr, stTemp->chName)) && (NULL != stTemp->next))
{
stPre = stTemp ;
stTemp = stTemp->next ;
}
//多个节点且第一个为所要删除的节点
if
(g_stHead == stTemp)
{
stTemp = g_stHead->next ;
free(g_stHead);
g_stHead = stTemp ;
printf("\n删除成功\n\n\r");
return OK;
}
if
(NULL == stTemp->next)
{
//多个节点且所要删除的节点是尾节点
//printf("%s\n",
stTemp->chName);
//printf("%s\n", chStr);
if (!(strcmp(chStr, stTemp->chName)))
{
stPre->next
= NULL ;
free(stTemp);
stTemp
= NULL;
printf("\n删除成功\n\n\r");
return
OK;
}
printf("未找到符合条件的节点\n\r");
return ERROR;
}
//多个节点且所要删除的节点是中间节点
stPre->next
= stTemp->next;
free(stTemp);
stTemp
= NULL;
printf("\n删除成功\n\n\r");
return
ERROR;
}
void Insert(void)
{
struct
STU *stNode = NULL;
stNode
= (struct STU *)malloc(LEN);
if
(NULL == stNode)
{
exit(-1) ;
}
memset(stNode,
0, sizeof(LEN));
printf("学生学号:");
scanf("%ld",&stNode->lNumber);
printf("学生姓名:");
scanf("%s",stNode->chName);
printf("语文成绩:");
scanf("%d",&stNode->iChinese);
printf("数学成绩:");
scanf("%d",&stNode->iMath);
//g_stHead
= p1;
struct
STU *stTemp = NULL;
//链表为空
if
(NULL == g_stHead)
{
g_stHead = (struct STU
*)malloc(sizeof(LEN));
if (NULL == g_stHead)
{
exit(-1)
;
}
memset(g_stHead, 0, sizeof(LEN));
strcpy(g_stHead->chName,
stNode->chName);
g_stHead->lNumber =
stNode->lNumber;
g_stHead->iChinese =
stNode->iChinese;
g_stHead->iMath = stNode->iMath;
}
//只有一个节点
else
{
if (NULL == g_stHead->next)
{
stTemp
= (struct STU *)malloc(sizeof(LEN));
if
(NULL == stTemp)
{
exit(-1);
}
memset(stTemp,
0, sizeof(LEN));
strcpy(stTemp->chName,
stNode->chName);
stTemp->lNumber
= stNode->lNumber;
stTemp->iChinese
= stNode->iChinese;
stTemp->iMath
= stNode->iMath;
g_stHead->next
= stTemp;
}
//多个结点
else
{
stTemp
= g_stHead;
while
(NULL != stTemp->next)
{
stTemp = stTemp->next;
}
stTemp->next
= (struct STU *)malloc(sizeof(LEN));
if
(NULL == stTemp->next)
{
exit(-1);
}
memset(stTemp->next,
0, sizeof(LEN));