reading assignment: Sudkamp, chapter 1. Introduction: what is a computer? what is a computer problem? examples of possible computer models: decision trees, quantum computers, Turing machines... alphabets words the empty word languages decision vs. search problems encoding of inputs as integers or as binary strings. e.g. Matrices, graphs,pictures. decision problems can be cast as language decidability problems. e.g. to decide whether a number is prime or not is the same problem as deciding whether a string belongs to the language "PRIMES".