Thanks 'LuckY' and 'major_small' your tips have solved my problem.
I was way out of the right path.... it seams that I've to buy some new books and trow my 10 year old college notes away.
This is how the code looks like now:
char *DT_Country = new char;
char *DT_Operator = new char;
source.open("Header.txt",ios::in | ios::nocreate);
source.getline(DT_Country, 20, '\n'); if (DT_Country=='\0') strcpy(DT_Country, "United States");
source.getline(DT_Operator,20,'\n'); if (DT_Operator=='\0') strcpy(DT_Operator, "T-Mobile")