_T的意思

_T:如果编译时指定生成UNICODE版本，则将字符串转换成UNICODE；如果编译是没有指定UNICODE，则就是一般的窄字符。

比如：

CString str;
str.FormatMessage(
_T("Checks the security descriptor on a named object.\n")
_T("\n")
_T("Usage: %1 [-?] [-at|-no_at] [-file|-regkey|-service|-kernel|-printer] [objectname]*\n")
_T(" -? Display this help message\n")
_T(" -at Examine the process access token (default)\n")
_T(" -no_at Don't examine the process access token\n")
_T(" -file objectname is the name of a file to examine (default)\n")
_T(" -regkey objectname is the name of a registry key to examine\n")
_T(" -service objectname is the name of a service to examine\n")
_T(" -kernel objectname is the name of a kernel object to examine\n")
_T(" these can be semaphores, events, mutexes, waitable timers, and file mappings\n")
_T(" -printer objectname is the name of a printer to examine\n")
_T(" objectname defaults to \\\\.\\A:\n")
_T("Example: %1 C:\\boot.ini\n")
_T("\n")
_T("Note: \\\\.\\A: is not the same as A:\n")
_T("Checking \\\\.\\A: checks access to the floppy drive,\n")
_T("Checking A: checks access to the root directory"),
path);