1. CSE115: Introduction to Computer Science I Dr. Carl Alphonce 219 Bell Hall 645-4739 alphonce@buffalo.edu 1

2. Announcements Cell phones off Name signs out and... 2

3. An apology I dropped the ball on coverage for the A7 recitation. You can complete the first-week exercises during the week, or during recitation next week. If you need any help completing them, just let me know. 3

4. Last class Instructions are encoded as bit strings Machine languages Fetch-Decode-Execute cycle 4

5. Computer Organization Central Processing Unit (CPU) –Registers General purpose (e.g. R1 – R16) Special purpose (e.g. Program Counter and Instruction Register) –Arithmetic Logic Unit (ALU) Memory 5

6. Roadmap (where we’re headed) Low-level languages High-level languages Requirements for a programming language 6

7. Low-level languages Machine language –1101000001000010 Assembly language –ADD R1 R2 7

8. Translation LLL  LLL is called assembly –there is a 1:1 translation from assembly to machine language –fairly simple process 8

9. High level languages Java (this is the language we will be using) –We can write “x + y” instead of “ADD R1 R2” (in addition to several MOV instructions) Others: C#, Erlang, Python, ML, Prolog, Lisp, etc. 9

10. Translation LLL  LLL is called assembly –there is a 1:1 translation from assembly to machine language –fairly simple process HLL  LLL is called compilation –there is no 1:1 translation –translation is quite complex –optimizations can be applied to make low level code more efficient 10

11. Requirements of a PL Sequencing Selection Repetition 11

12. Equivalences Computation models –Turing Machine –Lambda calculus Programming languages –Java –C# –Prolog –Python 12

13. High-level languages Richer syntax than –Machine language (bit strings) –Assembly language (mnemonic) Improved readability/writeability Must be translated (compiled) to machine language 13

14. Java A modern high-level language Object-oriented Large libraries (Relatively) simple core language 14

15. Questions? 15

16. Moving on… We will return to low-level issues later in the semester, and also in later courses. This brief low-level discussion gives context for upcoming topics. Now we turn to some higher-level issues.

17. I have a question for you! What did you have for breakfast today?

18. Activity The goal of this short activity is to demonstrate two things: 1.objects have behaviors 2.sending message to objects can trigger those behaviors