1. CS 330 PROGRAMMING LANGUAGES & SOFTWARE ENGINEERING Dr. Blaise W. Liffick Spring 2015 1

2. 2 Programming Techniques Languages Programming Environments Java C++ Problem Analysis Program Design Algorithms & Design Patterns Data Structures Paradigms Hardware Network Linux Eclipse

3. 3 Early Computers Late 1930’s, John Atanasoff, Clifford Berry ENIAC –1946 –University of Pennsylvania –J. Presper Eckert and John Mauchley –John von Neumann, stored-program concept

4. First Generation: 1940 – 1956 Vacuum tubes Scientific oriented ENIAC UNIVAC – first commercial computer 4

5. Second Generation: 1956 – 1963 Transistors replaced vacuum tubes I/O via punch cards and printers First “high-level” languages developed Data processing introduced 5

6. Third Generation: 1964 - 1971 Integrated circuit (semiconductors) Keyboards & monitors Time sharing Computer “families” Minicomputers vs. mainframes 6

7. Fourth Generation: 1971 – ? VLSI CPU on a chip: Microprocessor Microcomputers & Supercomputers 7

8. Fifth Generation: ??? Based on artificial intelligence Big “Fifth Gen” project by Japanese in 1980’s Voice recognition, parallel processing, superconductors 8

9. 9 Categories of Computers Supercomputers Mainframe Minicomputers Microcomputers Mobile devices Power Size Cost

10. 10 Computer Hardware CPU - central processing unit –Where decisions are made, computations are performed, and input/output requests are delegated Main Memory –Stores information being processed by the CPU Secondary Memory (Mass Storage) –Stores data and programs

11. 11 Computer Hardware Input devices –Allow people to supply information to computers Output devices –Allow people to receive information from computers Peripheral Devices –Generally I/O, mass storage Network connection –Modems –Ethernet interface

12. 12 Figure 1.2 Computer components Mass storage

13. 13 CPU “Brains” of the computer –Arithmetic calculations are performed using the Arithmetic/Logical Unit or ALU –Control unit decodes and executes instructions –Registers hold information and instructions for CPU to process Arithmetic operations are performed using binary number system

14. 14 Memory Stores –programs operating system applications –data Types –RAM - volatile –ROM Composed of bits, which are combined into bytes

15. 15 Memory Cells AddressContents -27.2 354 0.005 -26 H X 75.62 RTV 001... 0 1 2 3 4 5 6... 999

16. 16 Input / Output Devices Accessories that allow computer to perform specific tasks –Receiving information for processing –Return the results of processing Common input and output devices –Keyboard JoystickScanner –Printer MonitorSpeaker

17. 17 Computer Networks Allows multiple computers to connect together to share resources and/or data LAN - Local area network –Organizational WAN - Wide area network –Internet Requires additional hardware –modem –network interface –servers

18. The “Cloud” Wireless access –WiFi –Cell Servers –Storage –Applications 18

19. 19 World Wide Web Introduced 1989 Developed by CERN –European Laboratory for Particle Physics Web browser - GUI –Netscape –IE –Firefox

20. 20 1.3 Computer Software Operating system Other system software –utilities –programming language systems Applications

21. 21 Operating System E.g. Windows ®, Linux, Mac OS X, Unix ® Controls –the interaction of system with the user –hardware interactions Part is usually stored on ROM, rest on hard drive –This arrangement requires booting the system

22. 22 Some OS Responsibilities Communicating with the user; receiving user commands Managing allocation of memory, processor time, file system, and other resources Collecting input from keyboard, mouse, etc. Conveying output to screen, printer, etc. Writing data to secondary storage devices

23. 23 Application Software Does the “real” work Common application software –Word processors –Desktop publishing programs –Spreadsheets –Presentation managers –Drawing programs

24. 24 Programming Languages Machine Language –Most fundamental language of the computer –Unique for each processor type –Binary 0s and 1s that specify what to do 0010 0000 0000 0100 1000 0000 0000 0101 0011 0000 0000 0110

25. 25 Table 1.2 A Program in Machine and Assembly Language

26. 26 High - Level Languages Resemble human language –Java, C++, C, Pascal, FORTRAN, Ada a = a + b; More compact and human understandable than machine language Must be translated into machine language

27. 27 1.4 Processing a High-Level Language Program Set of programs used to develop software A key component is a translator –Compiler Examples –Java, g++, Microsoft Visual C++ ® Other programs needed –Editor –Linker –Loader IDE (e.g. Eclipse)

28. 28 Processing a Program Editor used to enter the program –Like minimal word processor –Creates source program file Compiler translates the source program –Displays syntax errors –Creates (usually) temporary object code file Linker/Loader to combine object file with other object files and execute program –Creates final executable program

29. 29 Executing a Program CPU –examines each program instruction in memory –sends out command signals required to carry out the instruction Special instructions used to –input data into memory for the program to use –output data to display or printer (or other device)

30. 30 Editor used to create program Source File Compiler translates program into machine language Error Messages unsuccessful Linker connects object files Object File Other Object Files Executable File successful Loader prepares for execution Compilers

31. 31 Editor used to create program Source File Compiler translates program into machine language Error Messages unsuccessful Java Runtime Environment Byte Codes Other Object Files successful.java.class Java

32. 32 1.5 Software Development Method 1.Problem Analysis –Identify data objects –Determine Input / Output data –Constraints on the problem 2.Design –Decompose into smaller problems –Top-down design (divide and conquer) –Develop Algorithm (Desk check) Algorithm refinement

33. 33 Software Development Method 3.Implementation Converting the algorithm into programming language 4.Testing –Verify the program meets requirements –System and Unit test 5.Maintenance –All programs undergo change over time

34. 34 Waterfall Software Development Lifecycle

35. 35 Spiral Software Development Lifecycle

36. 36 Iterative Software Development Lifecycle

37. Testing How? –Path coverage (impractical) –Statement coverage (imprecise) –Proof of correctness (also impractical) –Formal Testing Process 37

38. Types of Testing Design verification Unit testing Integration testing System testing Regression testing Top down vs. bottom up 38

39. Design Verification Tests the algorithms in pseudo-code form before any coding takes place. Uses the test plan for testing. 39

40. Unit Testing Software is typically developed in units – subprograms, methods, functions. Test each unit independently. Verifies the unit interface and basic functioning. Involves drivers. 40

41. Integration Testing Combines multiple units to test collectively. May involve not only drivers, but stubs. 41

42. System Testing Testing of multiple programs that collectively must work together. E.g. MS Office Suite 42

43. Regression Testing Retesting code previously tested. Done generally during maintenance updates to ensure that any change does not cause problems with other units or elements of a system. Gopher effect! 43

44. Top Down Development Testing begins with development of highest level units. Subunits are created as stubs, enabling the testing of unit interfaces only (not unit functionality). Helps ensure that the structure of the code is correctly implemented based on the design. 44

45. Bottom Up Development Follows unit testing technique – as each unit is implemented, it is immediately tested independently. Unit is fully developed functionally. Requires integration testing once enough units have been implemented and unit tested. 45

46. Developing a Test Plan Theoretically, a program’s specifications should be sufficiently defined for it to be possible to identify classes on inputs (both valid an invalid) and expected outputs. The collection of such classes is the Test Plan, which should be sufficient for ensuring the proper functioning of any software. 46

47. The Paradox of Testing It is impossible (impractical) to prove a program is correct, you can only prove it is incorrect! The goal of testing, then, is to try every trick possible to cause a program to either crash or produce erroneous or anomalous results – i.e. you try to show it has bugs. If you fail in showing that a program has bugs, then you conclude that the program is as bug-free as you can currently make it. 47

48. Components of a Test Plan Test Plan – a collection of test cases. Test Case – one instance of inputs from which the code will operate to some final state. Composed of –Unique identifier (number or name). –Description of the purpose of this test case – the type of test. –The data set for the test. –A detailed description of expected results. 48

49. Types of Test Cases Valid –Known inputs to produce known outputs –Typically what are given as examples in assignment specifications Invalid –Exceptions –Typically looking for anomalous input –ALL input should typically be accepted by the program, but only SOME of the input leads to successful processing. 49

50. Types of Test Cases, con’t Boundary values –Every condition in the code creates boundaries between what will trigger the condition either true or false. –Each boundary is an opportunity for errors to creep into the code (e.g. < versus <=). –Set up test cases to force every condition to trigger on either sides of each boundary. –E.g. if (0 <= exam && exam <= 100) 50

51. Types of Test Cases, con’t Constraints describe ranges and conditions of valid operational parameters –E.g. ranges of input or output values. Includes limits on resources –E.g. capacities of input or output, memory requirements, speeds of operation Constraints define additional boundary conditions Should include not only maximums, but minimums, e.g. empty files, missing data 51

52. Word Search Test Plan 52