scanf_s is specific to Microsoft compilers as you specified about visual studio express edition. It is the same as scanf, except it does not cause buffer overload.
int scanf_s(const char *format [, argument]...);
Format - The format of the incoming string
Argument - Optional variables to place the incoming data
Now check this program which will receive input on the line until the enter key is pressed and place the value into the variable. This is the same as scanf, except it is safe.
printf("Enter a letter");