The second mid-semester exam will begin with the discussion of codes particularly uniquely decipherable and instantaneous codes. Students should understand McMillan's theorem and Kraft's theorem and the relationship of instantaneous codes and the prefix property. In addition, you are responsible for knowing how to construct an optimal or Huffman code when the source has given probabilitties (or frequencies). We also covered definitions of I(p), information of an outcome, and entropy of a source. The noiseless coding theorem relates entropy and average codeword length for uniquely decipherable codes. We also discussed some initial aspects of noisy coding working mostly with the binary symmetric channel. You are responsible for doing some elementary calculations concerning the probability of undetected error with and without a parity check. Lastly we covered division of polynomials over a field F and paid particular attention to the case when F = Z/p the integers mod p, p a prime number. THE EXAM WILL BE OPEN BOOK, OPEN NOTES. The relevant material is contained in the following sections of the texts. In Garrett's notes we covered chaqpters 2, 3, sections 4.1 and 4.2, chapter 5, and sections 10.1 and 10.2. In Roman's text, we covered Chapters 1-3.