1. Computers: Tools for an Information Age
Chapter 15
Programming and Languages:
Telling the Computer What to Do

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 that are in use today
Explain the concepts of object-oriented programming

3. Programming
Program – a set of detailed, step-by-step instructions that directs the computer to do what you want it to do
Programming language – a set of rules that provides a way of telling the computer what operations to perform

4. The Programming Process
Five main steps
Defining the problem
Planning the solution
Coding the program
Testing the program
Documenting the program

5. Defining the Problem Develop a written agreement that specifies:
The input data
The desired output
The processing required to convert
Sometimes, the programmer receives a written specification from the systems analyst
Other times, the programmer meets with users directly
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6. Planning the Solution
Algorithm – a detailed, step-by-step solution to the problem
Several tools help plan the algorithm
Desk-check the solution
Carry out each step of the algorithm with pencil and paper
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7. Planning Tools Flowchart – a pictorial representation of the algorithm
Pseudocode – English-like language
Specifies algorithm with more precision than you can in English, but less than a programming language
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8. Coding the Program
Translating the algorithm from the planning stage into a formal programming language
All languages have syntax rules
Similar to grammatical rules
The computer will reject a program with even a minor syntax error
Programs can be keyed into the computer by using a text editor
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9. Testing the Program Two phases of testing the program Translation
Converting the program you wrote into the binary instructions the CPU understands
Debugging
Identifying and correcting logic errors in the program
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10. Translation
Compiler translates the program (source module) into a machine language version (object module)
If the compiler detects syntax errors, it will produce messages describing those errors
If no syntax errors exist, the object module will be linked to create a load module
Load module is executed by the computer
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11. Documenting the Program
Materials are generated at each part of the process
Common examples of documentation
Flowchart and/or pseudocode
Comments within the source code
Testing procedures
Layouts of input and output records
A narrative description of the program
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12. Levels of Languages
Lower-level languages – more like the 0s and 1s the computer itself uses
Higher-level languages – more like the languages people use
Divided into five generations

13. Five Generations of Languages
Machine language
Assembly languages
High-level languages
Very high-level languages
Natural languages

14. Machine Language
Programs and memory locations are written in strings of 0s and 1s
Problems with machine languages
Programs are difficult to write and debug
Each computer has its own machine language
Only option available to early programmers
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15. Assembly Languages Substitute mnemonic codes for 0s and 1s
For example, A for add, C for compare, etc.
Use names rather than binary addresses for memory locations
Require an assembler to translate the program into machine language
Still used for programming chips and writing utility programs
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16. High-Level Languages Transformed programming
Programmers could focus on solving problems rather than manipulating hardware
Programs could be written and debugged much more quickly
Requires a compiler to convert the statements into machine language
Each computer has its own version of a compiler for each language
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17. Very High-Level Languages
Also called fourth-generation languages (4GLs)
Considered nonprocedural languages
The programmer specifies the desired results, and the language develops the solution
Programmers can be about 10 times more productive using a fourth-generation language than a third-generation language
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18. Natural Languages Resemble written or spoken English
Programs can be written in a natural syntax, rather than in the syntax rules of a programming language
The language translates the instructions into code the computer can execute
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19. Major Programming Languages
FORTRAN
COBOL
BASIC
RPG
Visual Basic C
Java

20. FORTRAN The first high-level language Stands for FORmula TRANslator
Used primarily for engineering, mathematical, and scientific tasks
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21. COBOL Stands for COmmon Business-Oriented Language
Used primarily for business requirements
Processes large data files
Produces well-formatted reports
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22. BASIC Stands for Beginners’ All-Purpose Symbolic Instruction Code
Developed to teach programming to college students
Became very popular with the introduction of the microcomputer
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23. RPG Stands for Report Program Generator
Designed to allow rapid creation of reports
Programmer simply describes the source data and desired report format
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24. Visual Basic Allows programmer to create Windows-like user interfaces
Programmer drags a control (button, text box, etc.) onto the form
VB creates the code associated with that control
VB is event-driven
The user controls the program
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25. C Originally designed to write systems software
Offers the ease of use of a high-level language with the efficiency of an assembly language
Very portable – can be used with virtually every combination of computer and operating system
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26. Java
A network-friendly programming language that permits a piece of software to run directly on many different platforms
Allows programmers to write one version of the program, rather than a separate version of each platform
Very useful for Internet development
Java applets can run in the user’s Web browser
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27. Object-Oriented Programming
Object – a self-contained unit that contains both data and its related functions
Key terms in object-oriented programming
Encapsulation – an object isolates both its data and its related instructions
Attributes – facts that describe the object
Also called properties
Methods – instructions that tell the object to do something
Messages – an outside stimulus that results in the change of the state of an object

28. Using Objects Programmers define classes of objects
The class contains all attributes that are unique to objects of that class
An object is an instance (occurrence) of a class
Objects are arranged hierarchically in classes and subclasses
Subclasses are derived from classes
Inheritance – a subclass possesses all attributes of the class from which it is derived
Additional attributes can be coded in the subclasses

29. Activating the Object
A message is sent to the object, telling it to do something
The object’s methods tell it how to do it
Polymorphism – each object has its own way to process the message
For example, the class may have a Move method, but each subclass implements that method differently

30. Object-Oriented Languages
Java C#
Visual Basic

31. C++ An enhancement of the C language
Includes all features of C
Adds support for object-oriented programming
Can be used as simply an improvement of C, without the object-oriented features
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32. Java A pure object-oriented program
Used to create small programs called applets
Applets can be delivered over the Web and run on any platform
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33. C# Microsoft’s answer to Java
Has the same advantages over C++ that Java has
Designed to work within Microsoft’s .NET environment
.NET is designed for building, deploying, and running Web-based applications
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34. Visual Basic Previous versions supported some object technology
The current version, VB.NET, is the first to support inheritance and polymorphism
These two traits are required for a true object-oriented language
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