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Technical Trainers College – ICT Department

Introduction to Programming

Programming and Languages:Telling the Computer What to Do

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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

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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 do• Programming 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 uses• Higher-level languages – more like the languages people use• Divided into five generations

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

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Major Programming Languages• FORTRAN• COBOL• BASIC• PROLOG• Visual Basic• C, C++• Java

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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

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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

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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++• Java• C#• Visual Basic