2. CMPE13Cyrus Bazeghi 1 Programming Languages Telling computers what to do

3. CMPE132 Objectives Describe what programmers do and do not do Explain how programmers define a problem, plan the solution and then code, test, and document the program List and describe the levels of programming languages – machine, assembly, high level, very high level, and natural Describe the major programming languages in use today Explain the concepts of object-oriented programming

4. CMPE13 Program Set of instructions written in a programming language that tells the computer what to do 3

5. CMPE13 Programmers Prepare instructions that make up the program Run the instructions to see if they produce the correct results Make corrections Document the program Interact with –Users –Managers –Systems analysts Coordinate with other programmers to build a complete system 4

6. CMPE13 The Programming Process Defining the problem Planning the solution Coding the program Testing the program Documenting the program 5

7. CMPE13 The Programming Process: Defining the Problem What is the input What output do you expect How do you get from the input to the output 6

8. CMPE13 The Programming Process: Planning the Solution Algorithms –Detailed solutions to a given problem Sorting records, adding sums of numbers, etc.. Design tools –Flowchart –Pseudocode Has logic structure, but no command syntax Desk-checking –Personal code design walk through Peer Reviews –“Code walk through”/structured walk through 7

9. CMPE13 The Programming Process: Planning the Solution Accept series of numbers and display the average 8

10. CMPE13 The Programming Process: Coding the Program Translate algorithm into a formal programming language Within syntax of the language How to key in the statements? –Text editor –Programming environment Interactive Development Environment (IDE) 9

11. CMPE13 VI Mode editor, comes with pretty much all UNIX/LINUX distros Insert or command modes Cheat Sheet http://www.lagmonster.org/docs/vi.html 10

12. CMPE13 Emacs A very “rich” editor More than just an editor Cheat Sheet http://ccrma.stanford.edu/guides/packag e/emacs/emacs.html 11

13. CMPE13 The Programming Process: Testing the Program Translation – compiler –Translates from source module into object module –Detects syntax errors Link – linkage editor (linker) –Combines object module with libraries to create load module –Finds undefined external references Debugging –Run using data that tests all statements –Logic errors 12

14. CMPE13 The Programming Process: Documenting the Program Performed throughout the development Material generated during each step –Problem definitions –Program plan –Comments within source code –Testing procedures –Narrative –Layouts of input and output –Program listing 13

15. CMPE13 Choosing a Language Choice made for you –What is available? –Required interface What do you know best? Which language lends itself to the problem to be solved? 14

16. CMPE13 Language Generations Low levels closer to binary High levels closer to human code Five Generations: –Procedural Languages Machine language Assembly language High-level language – 3GL –Nonprocedural Languages Very high-level language – 4GL Natural language – 5GL 15

17. CMPE13 Machine Language Written in strings of 0 and 1 –Displayed as hexadecimal Only language the computer understands All other programming languages are translated to machine language Computer dependent 16

18. CMPE13 Assembly Language Mnemonic codes –Add, sub, tst, jmp… Names for memory locations Computer dependent “Assembler” translates from Assembly to machine language 17

19. CMPE13 3GL: High-Level Languages 1960s Languages designed for specific types of problems and used syntax familiar to the people in that field –FORTRAN: (FORmula TRANslator) Math –COBOL: (COmmon Business Oriented Language) Business Compile translates from high-level language to machine language 18

20. CMPE13 4GL: Very High-Level Languages Programmer specifies the desired results; the language develops the solution Ten times more productive with a 4GL than a procedural language Query Languages –Retrieve information from databases –Easy to learn and use 19

21. CMPE13 5GL: Natural Languages Resemble natural or spoken English Translates human instructions into code the computer can execute Commonly used by non-programmers to access databases 20

22. CMPE13 Third Generation Languages: Traditional Programming Describe data Describe procedures or operations on that data Data and procedures are separate 21

23. CMPE13 Third Generation Languages FORTRAN –1954 –Represent complex mathematical formulas –C/C++ has replaced FORTRAN COBOL –1959 –Business –Large complex data files –Formatted business reports 22

24. CMPE13 Average a list of numbers Accept series of numbers and display the average 23

25. CMPE13 Third Generation Languages FORTRAN 24

26. CMPE13 Third Generation Languages COBOL 25

27. CMPE13 Third Generation Languages BASIC (Beginners All-purpose Symbolic Instruction Code) –1965 –Popularity grew with PC popularity (1970s) –Easy to learn –Used little memory –Bill Gates beginnings.. MS Basic RPG –1965 –Report generation – quickly creates complex reports 26

28. CMPE13 Third Generation Languages BASIC 27

29. CMPE13 Third Generation Languages MS Visual Basic –1987 –Create complex user interfaces –Uses standard Windows features –Event-driven – user controls the program C –1972 –Efficient code – the language of UNIX –Portability C++ –Enhancement of C (Object Oriented) 28

30. CMPE13 Third Generation Languages C++ 29

31. CMPE13 OOP: Object-Oriented Programming Object –Self-contained unit of data and instructions –Includes Related facts (data) Related functions (instructions to act on that data) Example –Object:cat –Data:feet, nose, fur, tail –Functions:eat, purr, scratch, walk –Cat:Kitty, Tabby 30

32. CMPE13 OOP: Object-Oriented Programming Encapsulation – describes the objects self- containment Attributes – the facts that describe the object Methods / operations – the instructions that tell the object what to do Instance – one occurrence of an object Messages – activate methods –Polymorphism Example: A ‘walk’ message causes Kitty to move (in a cat-like way) 31

33. CMPE13 OOP: Object-Oriented Programming Class – defines characteristics unique to all objects of that class Inheritance – Objects of a class automatically posses all of the characteristics of the class from which it was derived Subclass – inherits characteristics from class and defines additional characteristics that are unique Instance – actual occurrence of an object 32

34. CMPE13 Example Class: Boat Subclass: Canoe Subclass: Powerboat Subclass: Sailboat Instance: Chardonnay II OOP: Object-Oriented Programming 33

35. CMPE13 OOP: Object-Oriented Programming Using Objects in Business Class:Customer Subclass:Retail or Wholesale Instance: John Smith Retail and Wholesale customers automatically inherit customer address since it is part of the Customer class 34

36. CMPE13 OOP: Object-Oriented Programming Languages C++ Can write both structured and object-oriented code Visual Basic Rudimentary features of object-oriented language 35

37. CMPE13 Third Generation Languages Java Cross-platform Java Virtual Machine (JVM) –Sits on top of computer’s regular platform –Translates compiled Java code into instructions for the specific platform Applets 36