Computers:Tools for an Information Age

Chapter 15Programming and Languages:Telling the Computer What to Do

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Objectives

Describe what programmers do and do not doExplain how programmers define a problem, plan the solution, and then code, test, and document the programList and describe the levels of programming languages: machine, assembly, high level, very high level, and naturalDescribe the major programming languages that are in use todayExplain the concepts of object-oriented programming

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Programming

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

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The Programming Process

Five main steps Defining the problem Planning the solution Coding the program Testing the program Documenting the program

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Levels of Languages

Lower-level languages – more like the 0s and 1s the computer itself usesHigher-level languages – more like the languages people useDivided into five generations

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Five Generations of Languages

Machine languageAssembly languagesHigh-level languagesVery high-level languagesNatural languages

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Major Programming Languages

FORTRANCOBOLBASICRPGVisual BasicCJava

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Object-Oriented Programming

Object – a self-contained unit that contains both data and its related functionsKey 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

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Using ObjectsProgrammers 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

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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

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Object-Oriented Languages

C++JavaC#Visual Basic