chapter 12: computer programming 1 computer programming chapter 12

Chapter 12: Computer Programming

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Computer Programming

Chapter 12


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Programming Basics

• Computer Programming and Software Engineering

• Programming Languages and Paradigms

• Program Planning

• Program Coding

• Program Testing and Documentation

• Programming Tools


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Computer Programming and Software Engineering

• The instructions that make up a computer program are sometimes referred to as code

• Programs can have millions of lines of code


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Computer Programming and Software Engineering


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Programming Languages and Paradigms

• Programming languages are made up of keywords and grammar rules designed for creating computer instructions

• Low-level languages

• High-level languages


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• First-generation languages

• Second-generation languages

• Third-generation languages


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• Fourth-generation languages

• Fifth-generation languages

• The Programming Paradigm


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Program Planning

• The problem 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

• Variables vs. constants


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Program Planning

• Problem statement:

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


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Program Coding

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


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Program Coding

• VDE (visual development environment)

– Form design grid– Control– Properties– Event– Event-

handling code


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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.


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Program Coding


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Program Testing and Documentation

• A computer program must be tested • Program errors include

– Syntax errors

– Runtime errors

– Logic errors

• Debugger


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Program Testing and Documentation

• Remarks/Comments


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Programming Tools

• SDK (software development kit)

• IDE (integrated development environment)


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Programming Tools

• Component

• API

• C and C++ are the most popular programming languages


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Procedural Programming

• Algorithms

• Expressing an Algorithm

• Sequence, Selection, and Repetition Controls

• Procedural Languages and Applications


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Algorithms

• What is an algorithm?

• Record steps to solve the problem

• Specify how to manipulate information

• Specify a solution


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Algorithms


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Expressing an Algorithm

• Pseudocode


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• Flowchart

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


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• Perform a walkthrough to make sure your algorithm works


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Sequence, Selection, and Repetition Controls

• Sequence control structure

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


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• Subroutines, procedures, and functions


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• Selection control structure

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


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• Repetition control structure

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


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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 algorithm

• Produces programs that run quickly and efficiently


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Object-Oriented Programming

• Objects and Classes

• Inheritance

• Methods and Messages

• Object-oriented Program Structure

• Object-oriented Languages and Applications


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Objects and Classes

• Object

• Class


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Inheritance

• What is inheritance?

– Superclass– Subclass– Class hierarchy


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Methods and Messages

• Method– Collect input, perform calculations, etc.– A method is activated by a message– Can be defined along with the class they

affect

• Polymorphism


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Object-Oriented Program Structure


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When the pizza programruns, on-screen promptsask for the shape, size, andprice of each pizza; thenthe program displays amessage that indicateswhich pizza is the bestdeal.


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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, C#, and Java

• The O-O paradigm results in decreased runtime efficiency, but allows encapsulation, which hides the internal details of objects and their methods


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Declarative Programming

• The Declarative Paradigm

• Prolog Facts

• Prolog Rules

• Input Capabilities

• Declarative Languages and Applications


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The Declarative Paradigm

• Attempts to describe a problem without specifying exactly how to arrive at a solution


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Secure Programming

• Black Hat Exploits

• Secure Software Development

• Mitigation


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Black Hat Exploits

• Today’s operating systems, utilities, and application software are full of defects that create security holes, which are exploited by black hats

• Buffer overflow


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Black Hat Exploits


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Black Hat Exploits

• Verbose error messages can also present attackers with information about the directory location of programs or files, the structure of a database, or the layout of the program in memory


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Secure Software Development

• Most software security problems can be traced back to defects that programmers unintentionally introduce in software during design and development

• Formal methods help programmers apply rigorous logical and mathematical models to software design, coding, testing, and verification

• Threat modeling (risk analysis) – used by security designer to determine (1) what are important issues the designer cares about and (2) a description of a set of security aspects (possible attacks to consider)


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• An attack tree is a hierarchical diagram of potential attacks against a system


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Secure Software Development• Defensive programming (AKA secure

programming)

– Source code walkthroughs– Simplification– Filtering input


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• Signed code


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Mitigation• Despite defensive programming and other

tactics to produce secure software, some defects inevitably remain undiscovered in products that end up in the consumers’ hands. When bugs are discovered, the programmer’s remaining line of defense is to produce a bug fix, or patch


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Mitigation

• Take the following steps to avoid security problems that stem from software defects– Select applications from software publishers

with a good security track record– Watch for patches and apply them– Consider using open source software, which

has been extensively reviewed by the programming community

– Keep your firewall and antivirus software deployed and up-to-date


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Chapter 12 Complete

Computer Programming

chapter 12: computer programming 1 computer programming chapter 12

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