You can't.
char[256] is a pointer to a char, and if you did a switch, you would be checking the address of a char (the 1st element of an array of chars). So input would be interpreted as something like 23847981 (the address of the first char), instead of whatever the user typed in. You could do:
But that would only check the first letter of input, so you still have to use strcmp(input, "asdf") to check the input of a string.Code:switch(*input) { }