I think a database is a bit of an overkill for a user list.
Create a binary file and a record for each user, and then read/write this to a file. If you have a lot of users and think this is slow, you can jus index the file.
Code:
#define NAME_SZ 50
typedef struct UserData{
char achName[NAME_SZ];
short sType;
}USER_DATA;
int addUser(char *achFile, USER_DATA *ud){
int iData, iIx;
if((iData=_open(achFile, _O_BINARY|_O_CREAT|_O_APPEND|_O_RDWR)) &&
(iIx=_open(achFile, _O_BINARY|_O_CREAT|_O_APPEND|_O_RDWR))){
_write(iData, ud, sizeof(USER_DATA));
_write(iIx, ud->achName, NAME_SZ);
_close(iData);
_close(iIx);
return(1);
}else
return(0);
}