The switch can be made on
1. the variable "s"
2. the read operation "getchar()"
There is no mechanism for rewind of
no look ahead and no way to store the input internally.
The program halts when getchar returns
There are two possibilities
What can we do with such a language?
Consider the following *UNIX operation
The patterns allowed are called regular expressions
The simple model that we have just
defined can recognize