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Programming Languages: Telling the Computers What to Do

Programming Languages: Telling the Computers What to Do. Chapter 16. 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

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Programming Languages: Telling the Computers What to Do

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  1. Programming Languages: Telling the Computers What to Do Chapter 16

  2. 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

  3. Contents • Program • Programmers • The Programming Process • Choosing a Language • Traditional Programming • Object-Oriented Programming • Learning to Program

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

  5. 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

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

  7. The Programming ProcessDefining the Problem • What is the input • What output do you expect • How do you get from the input to the output

  8. The Programming ProcessPlanning the Solution • Algorithm – detailed solution to a problem • Design tools • Flowchart • Pseudocode • Desk-checking • Structured walkthrough

  9. The Programming ProcessPlanning the Solution Accept series of numbers and display the average

  10. The Programming ProcessPlanning the Solution Accept series of numbers and display the average

  11. The Programming ProcessCoding the Program • Translate algorithm into a formal programming language • Syntax • How to key in the statements? • Text editor • Programming environment – Interactive Development Environment (IDE)

  12. The Programming ProcessTesting 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

  13. The Programming ProcessTesting the Program

  14. The Programming ProcessDocumenting 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

  15. 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?

  16. 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

  17. Machine Language • Written in strings of 0 and 1 • Only language the computer understands • All other programming languages are translated to machine language • Computer dependent

  18. Assembly Language • Mnemonic codes • Names for memory locations • Computer dependent • Assembler translates from Assembly to machine language

  19. 3GLHigh-Level Languages • 1960s • Languages designed for specific types of problems and used syntax familiar to the people in that field • FORTRAN: math • COBOL: business • Compile translates from high-level language to machine language

  20. 4GLVery 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

  21. 5GLNatural Languages • Resemble natural or spoken English • Translates human instructions into code the computer can execute • Commonly used by non-programmers to access databases

  22. Third Generation LanguagesTraditional Programming • Describe data • Describe procedures or operations on that data • Data and procedures are separate

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

  24. Third Generation Languages FORTRAN

  25. Third Generation Languages COBOL

  26. Third Generation Languages • BASIC • 1965 • Popularity grew with PC popularity (1970s) • Easy to learn • Used little memory • RPG • 1965 • Report generation – quickly creates complex reports

  27. Third Generation Languages BASIC

  28. Third Generation Languages • Visual Basic • 1987 • Create complex user interfaces • Uses standard Windows features • Event-driven – user controls the program • C • 1972 • Efficient code • Portability • C++ • Enhancement of C

  29. Third Generation Languages C++

  30. OOPObject-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, Susan

  31. OOPObject-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 Example: A walk message causes Kitty to move

  32. OOPObject-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

  33. OOPObject-Oriented Programming Example Class: Animal Subclass: Cat Subclass: Persian cat Instance: Kitty Objects can be reused

  34. OOPObject-Oriented Programming Languages • C++ Can write both structured and object-oriented code • Visual Basic Rudimentary features of object-oriented language

  35. 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. OOPObject-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

  37. Learning to Program • Enroll in courses • Read • Use tutorials • View Sample code • Write code (start small) • Use Help

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