刚学习C语言，很多东西都是似懂非懂的，这个源代码看的云里雾里的，希望高手讲解下，或者给个结构图帮助我理解下。。谢谢了


 #include<CONIO.H>   
#include<STDIO.H>   
#include<PROCESS.H>   
#include<STRING.H>   
#include<DOS.H>   
#define Brand struct brand   
#define Item struct item   
Brand   /*商品品牌类 */   
{   
   char  szBrndName[20];  /*名称*/   
   int   nBrndCode;      /*代码*/   
   int   nBrndQuan;   /*数量*/   
   float  flBrandPrice;   /* 价格*/   
};   
Item  /*商品种类类*/   
{   
   char szItemName[10];  /*名称*/   
   int nItemCode;            /*代码*/   
   char szColour[10];       /*颜色*/   
   int nItemQuan;          /* 数量*/   
   Brand strBrnd[3];        /*品牌*/   
};   
   
void GetBrandData_f(Brand *); /*输入商品品牌*/   
void ShowBrandData_f(Brand *); /*显示商品品牌*/   
void AddItem_f();     /*增加商品种类*/   
void RemoveItem_f();  /* 去掉商品种类*/   
void  SearchItem_f();    /* 查询商品种类*/   
void ShowAllBr_f();    /*显示种类清单*/   
void GetItemData_f( Item *);  /* 输入商品种类*/   
void ShowItemData_f(Item *); /*显示商品种类*/   
   
/*      GET Brand DATA    */   
/*  gets data about the Brandt it temperary storage */   
void  GetBrandData_f(Brand *strpBr)   
{   
   getchar();
   sin(10);
   printf("\n\nEnter Brand Name ");   
   gets(strpBr->szBrndName);   
   printf("\nEnter Brand Code ");   
   scanf("%d", &strpBr->nBrndCode);   
   printf("\nEnter Quantity ");   
   scanf("%d", &strpBr->nBrndQuan);   
   printf("\nEnter Price");   
   scanf("%f", &strpBr->flBrandPrice);   
}   
/*   SHOW Brand DATA   */   
/*  shows the data of the Brand */   
void ShowBrandData_f(Brand *strpBr)   
{   
   printf("\n\nName          :  ");   
   puts(strpBr->szBrndName);   
   printf("\n\nCode          :  ");   
   printf("%d", strpBr->nBrndCode);   
   printf("\n\nQuantity      :  ");   
   printf("%d", strpBr->nBrndQuan);   
   printf("\nPrice           :  ");   
   printf("%f", strpBr->flBrandPrice);   
}   
/*  GET Item DATA     */   
/* gets data about the Item it is temporary storage      */   
void  GetItemData_f(Item *strpIm)   
{   
   getchar();   
   printf("\nEnter Item Name ");   
   gets(strpIm->szItemName);   
   printf("\nEnter Item Code  ");   
   scanf("%d", &strpIm->nItemCode);   
   getchar();   
   printf("\nEnter Colour ");   
   gets(strpIm->szColour);   
   printf("\nEnter Quantity ");   
   scanf("%d", &strpIm->nItemQuan);   
   printf("\n\nEnter Brand 1 ");   
   GetBrandData_f(&strpIm->strBrnd[0]);   
   printf("\n\nEnter Brand 2 ");   
   GetBrandData_f(&strpIm->strBrnd[1]);   
   printf("\n\nEnter Brand 3 ");   
   GetBrandData_f(&strpIm->strBrnd[2]);   
}   
/*  SHOW Item DATA    */   
/* shows data about the Item */   
void ShowItemData_f(Item *strpIm)   
{   
   printf("\n\n\t\tItem Data");   
   printf("\n\nItem Name    :  ");   
   puts(strpIm->szItemName);   
/* 写一个字符串到标准的输出流（或缓冲区）-Write a string to stdout */   
   printf("\n\nItem Code    :  ");   
   printf("%d", strpIm->nItemCode);   
   printf("\n\nColour   :  ");   
   puts(strpIm->szColour);   
   printf("\n\nQuantity     :  ");   
   printf("%d\n",strpIm->nItemQuan);   
   getch();   
    /*  clrscr(); */   
   printf("\n\nBrand 1\n");   
   ShowBrandData_f(&strpIm-> strBrnd[0]);   
   getch();   
      /*  clrscr(); */   
   printf("\n\nBrand 2\n");   
   ShowBrandData_f(&strpIm-> strBrnd[1]);   
   /*  clrscr(); */   
   printf("\n\nBrand 3\n");   
   ShowBrandData_f(&strpIm-> strBrnd[2]);   
}   
/*  Add Item    */   
/* this function first gets data into temp storage then  saves it on the hard disk */   
void AddItem_f()/*将新增商品写到数据文件中*/   
{   
  /* clrscr(); */   
   Item strSamp;   
   FILE  *fp;   
   if((fp=fopen( "TIS.txt", "ab"))==NULL)   
   {    /* if file could not be opened */   
       printf("Error Could Not Open File" );   
       getch();   
       exit(1);   
   }   
   GetItemData_f(&strSamp);       /* Get Data From User For Temp. Storage */   
   /*    write data to hard disk */   
   fwrite((char *)&strSamp, sizeof(Item), 1, fp);   
   fclose(fp);   
}   
/*           TRAVERSE    */   
/*  this function shows the list of all the Brands */   
void ShowAllBr_f() /*显示数据文件中的所有商品种类及品牌*/   
{   
    /* clrscr(); */   
   Item strSamp;   
   FILE  *fp;   
   if((fp=fopen( "TIS.txt", "rb"))==NULL)   
   {    /* if file could not be opened */   
    printf("Error Could Not Open File" );   
    getch();   
    exit(1);   
   }   
   fread((char *)&strSamp, sizeof(Item), 1, fp);   
   /* Store Data In Object */   
   while( !feof(fp) ) /* Untill Contacts Present */   
   {   
       ShowItemData_f(&strSamp) ;  /* Display on Screen */   
       getch();      /* Wait For Keyboard Input */   
       fread((char *)&strSamp, sizeof(Item), 1, fp);  /* Read Next Contact */   
   }   
   fclose(fp);   
}   
/*  SEARCH   */   
void SearchItem_f()/*按商品的名称或代码查询商品*/   
{   
  char szImName[10];   
  FILE *fp;   
  int nImCode;   
  int nChoice;   
  int nFlag=0;      /* nFlag To Check If Found */   
  Item strSamp;   
  printf("\n(1)Search By Name\n(2)Search By Code");   
  scanf("%d", &nChoice);   
  if(nChoice==1)   
  {   
     getchar();   
     printf("\nEnter Item name  ");   
     gets(szImName);   
     nImCode=0;   
  }   
  else   
  {   
     printf("\nEnter Code of Item To Search  ");   
     scanf("%d", &nImCode);   
     strcpy(szImName,"null");   
  }   
  if((fp=fopen( "TIS.txt", "rb"))==NULL)   
  {    /* if file could not be opened */   
     printf("Error Could Not Open File" );   
     getch();   
     exit(1);   
  }   
  fread((char *)&strSamp, sizeof(Item), 1, fp);   
  /* Read Data To Object */   
  while( !feof(fp) )  /* Untill There Are Contacts */   
  {   
      if((strcmp(strSamp.szItemName, szImName)==0) || (strSamp.nItemCode==nImCode))   
      /*Compare */   
      {   
      ShowItemData_f(&strSamp);   
      getch();   
      nFlag=1;   /* Set Flag */   
      break; /* Break Loop */   
       }   
       fread((char *)&strSamp, sizeof(Item), 1, fp);   /* Read Next Contact */   
   }   
   if(nFlag !=1)  /* If Not Found */   
   {   
       printf("Item Not Found");   
       getch();   
   }   
   fclose(fp);   
}   
/* REMOVE Item  */   
/*  从数据文件中去掉某一品种。将商品数据文件拷贝到一临时文件中（要去掉的商品不拷贝），然后再将临时文件的所有内容写回到原数据文件*/   
void RemoveItem_f()   
{   
    FILE *fp, *ftemp;   
    char szImName[10];   
    int nImCode;   
    int nChoice;   
    Item strSamp;   
    printf("\n(1)Delete By Name\n(2)Delete By Code");   
    scanf("%d",&nChoice);   
    if(nChoice==1)   
    {   
    getchar();   
    printf("\nEnter Item name  ");   
    gets(szImName);   
    nImCode=0;   
    }   
    else   
    {   
     printf("\nEnter Code of Item To Search  ");   
     scanf("%d", &nImCode);   
     strcpy(szImName,"null");   
    }   
    if((fp=fopen( "TIS.txt", "rb"))==NULL)   
    {    /* if file could not be opened */   
    printf("Error Could Not Open File" );   
    getch();   
    exit(1);   
    }   
    if((ftemp=fopen("delete.txt", "wb"))==NULL)   
    {    /* if file could not be opened */   
     printf("Error Could Not Open File" );   
     getch();   
     exit(1);   
    }   
    fseek(fp,0,0);   
    fseek(ftemp,0,0);   
    fread((char *)&strSamp, sizeof(Item), 1, fp);   
    while(  !feof(fp) )   
    {   
    if( (strcmp(szImName, strSamp.szItemName)==0)  || (nImCode==strSamp.nItemCode))   
    {   
        fread((char *)&strSamp, sizeof(Item), 1, fp);   
    }   
    else   
    {   
        fwrite((char *)&strSamp, sizeof(Item), 1, ftemp);   
        fread((char *)&strSamp, sizeof(Item), 1, fp);   
    }   
    }   
    fclose(fp);   
    fclose(ftemp);   
    if((fp==fopen( "TIS.txt", "wb"))==NULL)   
    {    /* if file could not be opened */   
    printf("Error Could Not Open File" );   
    getch();   
    exit(1);   
    }   
    if((ftemp==fopen("delete.txt", "rb"))==NULL)   
    {    /* if file could not be opened */   
    printf("Error Could Not Open File" );   
    getch();   
    exit(1);   
    }   
    fseek(fp,0,0);   
    fseek(ftemp,0,0);   
    fread((char *)&strSamp, sizeof(Item), 1, ftemp);   
    while( !feof(ftemp) )   
    {   
     fwrite((char *)&strSamp, sizeof(Item), 1, fp);   
     fread((char *)&strSamp, sizeof(Item), 1, ftemp);   
    }   
    fclose(fp);   
    fclose(ftemp);   
}   
/*  MAIN FUNCTION */   
void main()   
{   
    Item strSamp;   
    int nChoice;   
    while(1)   
    {   
     printf("\n\tThe Inventory  System (TIS)");   
     printf("\n\n(1)Add Item\n\n(2)Show All Data");   
     printf("\n\n(3)Search Item\n\n(4)Remove Item\n\n(5)Exit TIS");   
     printf("\n\nEnter Choice ");   
     scanf("%d", &nChoice);   
     switch(nChoice)   
     {   
        case 1:   
           AddItem_f();   
           break;   
        case 2:   
           ShowAllBr_f();   
           break;   
        case 3:   
           SearchItem_f();   
           break;   
        case 4:   
           RemoveItem_f();   
           break;   
        case 5:   
           {   
         exit(1);   
        }   
           }   
    }   
}