void search_name()
{ struct telephone message[N];
  struct telephone mes;
  char reply='y';
  char found='y';
  struct telephone client_name;
  struct telephone amend_name[20];
  char client_address;
  FILE*fp;
  while(reply=='y')
  { found='n';
    fp=fopen("message.dat","r+w");
    if (fp!=NULL)
    { system("cls");
      printf("\n请输入您要查找的姓名：");
      scanf("%c",amend_name);
      while ((fread(&mes,sizeof(struct telephone),1,fp))==1)
        { if((strcmp(amend_name,mes.client_name))==0)
          { found='y';
            break;
           }
        }
调试出现错误：error C2664: 'strcmp' : cannot convert parameter 1 from 'struct telephone [20]' to 'const char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
Error executing cl.exe.

amend_name最好定义成char型：char amend_name[20];
获取姓名最好是
scanf("%s",amend_name);

if((strcmp(amend_name,mes.client_name))==0)

调试出现：
Linking...
44.obj : error LNK2001: unresolved external symbol "struct telephone __cdecl message(void)" (?message@@YA?AUtelephone@@XZ)
Debug/44.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.
是怎么回事？

[此贴子已经被作者于2016-6-28 14:53编辑过]

函数未定义。
问问题最好给完整的代码，猜起来很费劲。

怎么能把字符串赋值给一个结构呢