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 2

3. Last class Instructions are encoded as bit strings Machine languages Fetch-Decode-Execute cycle Assembly languages 3

4. Today’s lessons High-level languages Requirements for a programming language 4

5. Low-level languages Machine language –1101000001000010 Assembly language –ADD R1 R2 5

6. High level languages Java –We can write “x + y” instead of “ADD R1 R2” (in addition to with several MOV instructions) Others: C#, Erlang, Python, ML, Prolog, Lisp, etc. 6

7. 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 7

8. Requirements of a PL Sequencing Selection Repetition 8

9. Equivalences Computation models –Turing Machine –Lambda calculus Programming languages –Java –C# –Prolog –Python 9

10. High-level languages Richer syntax than –Machine language (bit strings) –Assembly language (mnemonic) Improved readability/writeability Must be translated (compiled) to machine language 10

11. Java A modern high-level language Object-oriented Large libraries (Relatively) simple core language 11

12. Questions? 12

13. 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.

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