Chapter 12

Computer ProgrammingComputer Programming

Chapter 12Chapter 12

Chapter 12: Computer Programming 2

12 Chapter Contents Section A: Programming Basics Section B: Procedural Programming Section C: Object-Oriented Programming Section D: Declarative Programming Section E: Secure Programming


12 SECTION AProgramming BasicsProgramming Basics

Computer Programming and Software Engineering

Programming Languages and Paradigms Program Planning Program Coding Program Testing and Documentation Programming Tools


12 Computer Programming and Software Engineering

The instructions that make up a computer program are commonly referred to as codecode

Programs can have millions of lines of code– Developed by computer programmers (or

software engineers)… programming– Typically stored as a file until it is needed

• Compile• Execute

SourceSource code vs. executableexecutable code


12 Computer Programming and Software Engineering


12 Programming Languages and Paradigms

Programming languages are made up of keywordskeywords and grammar rulesgrammar rules designed for creating computer instructions– Keywords can be combined with parameters

Low-level languagesLow-level languages typically include commands specific to a particular CPU or microprocessor family

High-level languagesHigh-level languages use command words and grammar based on human languages



First-generation languages– Machine language

Second-generation languages– Assembly language

Third-generation languages– Easy-to-remember command words



Fourth-generation languages– More closely resembles human language

Fifth-generation languages– Based on a declarative programmingdeclarative programming paradigm– Or, use of graphics/visual tools

The programming paradigmparadigm refers to a way of conceptualizing and structuring the tasks a computer performs




12 Program Planning The problem statementproblem statement defines certain

elements that must be manipulated to achieve a result or goal

You accept assumptions as true to proceed with program planning

Known information helps the computer to solve a problem

VariablesVariables vs. constantsconstants Inputs Inputs and Outputs Outputs


12 Program Planning Problem statement:

Assuming that there are two pizzastwo pizzas to compare, that both pizzas contain the same toppingssame toppings, and that the pizzas could be round or squareround or square, and given the prices, shapes, and sizesprices, shapes, and sizes of the two pizzas, the computer will print a message indicating which pizza has the lower price per which pizza has the lower price per square inchsquare inch


12 Program Coding

A text editortext editor such asNotepad allows programmersto enter lines of code using a familiar word processing interface.

A program editorprogram editor offers an edit/update environment specific to programming tasks in a given language.


12 Program Coding A VDE (visual development environmentvisual development environment) provides

programmers with tools to build substantial sections of a program– Form design grid– Control– Properties– Event– Event-Event-

handling handling codecode

Event-driven paradigm


12 Program Coding

Controls, such as theBest Deal button, can beselected by a programmerfrom a properties list. Here a programmer is selecting the background color for the Best Deal button.


12 Program Coding


12 Program Testing and Documentation

A computer program must be tested to ensure that it works correctly

Program errors include– Syntax errorsSyntax errors– Runtime errorsRuntime errors– Logic errorsLogic errors

A debuggerdebugger can help a programmer read through lines of code and solve problems


12 Program Testing and Documentation

Remarks or “comments” are a form of documentationdocumentation that programmers insert into the program code


12 Programming Tools An SDK (software development kitsoftware development kit) is a

collection of language-specific programming tools that enables a programmer to develop applications for a specific computer platform

An IDE (integrated development integrated development environmentenvironment) is a type of SDK that packages a set of development tools into a sleek programming application– Program editor, syntax checker, compiler,

debugger, GUI tools, etc.


12 Programming Tools A componentcomponent is a program module, typically

designed to accomplish a specific task An APIAPI is a set of application program or operating

system functions that programmers can access from within the programs they create– For example, the Windows XP API

C and C++C and C++ are the most popular programming languages– Operating Systems such as Windows, Linux, etc.– Productivity applications– Web server applications– Games


12 SECTION BProcedural ProgrammingProcedural Programming

Algorithms Expressing an Algorithm Sequence, Selection, and Repetition Controls Procedural Languages and Applications


12 Algorithms Set of stepssteps for carrying out a task that can

be written down and implemented Start by recording the steps you take to solve

the problem manually Specify how to manipulate data Specify what the algorithm should display/do

as a solution

INPUT PROCESS OUTPUT


12 Algorithms


12 Expressing an Algorithm Structured English PseudocodePseudocode


12 Expressing an Algorithm Flowchart

The pizza program flowchartillustrates how the computershould proceed through theinstructions in the final program.


12 Expressing an Algorithm Perform a

walkthroughwalkthrough to make sure your algorithm works


12 Sequence, Selection, and Repetition Controls

Sequence controlSequence control structure

Executing a GOTO commanddirects the computer to a differentpart of the program.



Subroutines, procedures, and functions are sections of code that are part of the program, but not included in the main main sequential sequential execution pathexecution path



Selection controlSelection control structure

The computer executes a decisionindicated on the flowchart by the question in the diamond shape.



Repetition controlRepetition control structure

To execute a looploop, the computerrepeats one or more commands until some condition indicates that the looping should stop.


12 Procedural Languages and Applications

Popular procedural languages include FORTRAN, COBOL, FORTH, APL, ALGOL, PL/1, Pascal, C, Ada, and BASIC

The procedural approach is best used for problems that can be solved by following a step-by-step algorithmstep-by-step algorithm– Does not fit well with certain types of problems

Produces programs that run quickly and efficiently


12 SECTION CObject-Oriented ProgrammingObject-Oriented Programming

Objects and Classes Inheritance Methods and Messages Object-oriented Program Structure Object-oriented Languages and Applications


12 Objects and Classes An objectobject represents an abstract or real-world

entity A classclass is a template for a group of objects

with similar characteristics– A class attribute defines the characteristics of a

set of objects• Public vs. private

attributes


12 Object-Oriented Languages and Applications

SIMULA was believed to be the first object-oriented computer language

The Dynabook project was the second major development in object-oriented languages

Popular object-oriented languages today are Ada95, C++, Visual Basic, and C#C++, Visual Basic, and C#

The OO paradigm results in decreased runtime decreased runtime efficiencyefficiency, but allows encapsulation, which hides the internal details of objects and their methods

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