How to use characters in strings outside of the printable ASCII range?
When you initialize a string like that, you are specifying one character at a time. One character can only hold a value between 0 and 255. If you want to fill more bytes of your string, just specify more characters in the initializer:

char myString[4] = "\x06\x60\x44";


Note that unspecified characters are not guaranteed to be filled with 0's, although one 0 will be placed at the end of whatever you specify as the initializer:

char string2[8] = "test";


Five characters will be initialized, characters 6 through 7 might contain garbage.