introduction

introduction of computation is an extremely abbreviated look at some of the important ideas of the general areas of automata theory, compatibility, and formal languages. In various respects, this can be thought of as the elementary foundations of much of computer science.The area also includes a wide variety of tools,and general categories of tools. The classical theory of computation traditionally deals with processing an input string of symbols into an output string of symbols. Note that in the special case where the set of possible output strings is just {‘yes’, ‘no’}, (often abbreviated {T, F} or {1, 0}), then we can think of the string processing as string (pattern) recognition.We define:
1. An alphabet is a finite set of symbols.2. A string over an alphabet A is a finite ordered sequence of symbols from A.Note that repetitions are allowed. The length of a string is the number of symbols in the string, with repetitions counted. (e.g., |aabbcc| = 6) 3. The empty string, denoted by , is the (unique) string of length zero. Note that the empty string  is not the same as the empty set ;4. If S and T are sets of strings, then ST = {xy| x 2 S and y 2 T}