Chapter 13: Computer Programs and Programming Language

Computer Programs and Programming Languages

• A computer program is a series of instructions that directs a computer to perform tasks.
• Created by a programmer using a programming language.

Low‐Level Languages

• Machine language is the first generation of programming languages.
• Only language the computer directly recognizes.
• Assembly language is the second generation of programming languages.
• Programmer writes instructions using  symbolic instruction codes.
• A source program contains the code to be converted to machine language.

Procedural Languages

• In a procedural language, the programmer writes instructions that tell the computer what to accomplish and how to do it.
• Third-generation language (3GL)
• A compiler translates an entire program before executing it.
• An interpreter converts and executes one code statement at a time.
• The C programming language is used to write many of today’s programs.
• COBOL (COmmon Business-Oriented Language) is designed for business applications, but easy to read because of the English-like statements.

Object-Oriented Programming Languages and Program Development Tools

• An object-oriented programming (OOP) language allows programmers the ability to reuse and modify existing objects.
• Other advantages include:
• objects can be reused
• programmers create applications faster
• work well in a RAD environment
• most program development tools are IDEs
• Java is an object-oriented programming language developed by Sun Microsystems.
• The Just-in-time (JIT) compiler converts the bytecode into machine-dependent code.
• The Microsoft .NET Framework allows almost any type of program to run on the Internet or an internal business network, as well as computers and mobile devices.
• Features include:
• CLR (Common Language Runtime) 
• Classes
• C++ is an extension of the C programming language.
• C# is based on C++ and was developed by Microsoft.
• F# combines the benefits of an object-oriented language with those of a functional language.
• Visual Studio is Microsoft’s suite of program development tools:
• Visual Basic is based on the BASIC programming language
• Visual C++ is based on C++
• Visual C# combines the programming elements of C++ with an easier, rapid-development environment]
• A visual programming language is a language that uses a visual or graphical interface for creating all source code.
• Borland’s Delphi is a powerful program development tool that is ideal for building large-scale enterprise and Web applications in a RAD environment.
• PowerBuilder is a powerful program development RAD tool.
• Best suited for Web-based, .NET, and large-scale enterprise object-oriented applications.

Other Programming Languages and Development Tools

• A 4GL (fourth-generation language) is a nonprocedural language that enables users and programmers to access data in a database.
• One popular 4GL is SQL
• Classic programming languages include:
• Ada
• ALGOL
• APL
• BASIC
• Forth
• FORTRAN
• HperTalk
• LISP
• Logo
• Modula-2
• Pascal
• PILOT
• PL/1
• Prolog
• RPG
• Smalltalk
• An application generator is a program that creates source code or machine code from a specification of the required functionality.
• Often bundled as part of a DBMS
• A macro is a series of statements that instructs an application how to complete a task.
• You usually create the macro in one of two ways:
• Record the macro with a macro recorder
• Write the macro

Web Page Development

• HTML is a special formatting language that programmers use to format documents for display on the Web.
• XHTML is a markup language that allows Web sites to be displayed more easily on mobile devices.
• XML allows Web developers to create customized tags and use predefined tags to display content appropriately on various devices.
• WML is a subset of XML and is used to design pages for microbrowsers.
• Two applications of XML are RSS 2.0 and ATOM.
• Web browsers can execute short programs to add interactive elements to Web pages.
• To send and receive information between your computer and a Web server, these programs use the CGI (common gateway interface).
• Programmers write scripts, applets, servlets, or ActiveX controls using a variety of languages:
• JavaScript
• Perl
• PHP
• Rexx
• Tcl
• VBScript
• Dynamic HTML  (DHTML) allows Web developers to include more graphical interest and interactivity.
• Cascading style sheets (CSS) contain the formats for how a particular object should be displayed.
• Ruby on Rails (RoR) provides technologies for developing object-oriented, database-driven Web sites.
• Web 2.0 allows Web sites to provide a means for users to:
• Share personal information
• Allow users to modify Web site content
• Have application software built into the site
• Most Web 2.0 sites use APIs
• An API enables programmers to interact with an environment such as a Web site or operating system.
• Web page authoring software can create sophisticated Web pages that include images, video, audio, animation, and other effects
• Dreamweaver
• Expression Web
• Flash
• SharePoint Designer

Multimedia Program Development

• Multimedia authoring software allows programmers to combine text, graphics, animation, audio, and video in an interactive presentation.
• ToolBook
• Director
• Program development consists of a series of steps programmers use to build computer programs.

Step 1 – Analyze Requirements

• To initiate program development, programmer:
• Reviews the requirements
• Meets with the systems analyst and users
• Identifies input, processing, and output
• IPO chart

Step 2 – Design Solution

• Design a solution algorithm.
• In structured design, the programmer typically begins with a general design and moves toward a more detailed design.
• Programmers use a hierarchy chart to show program modules graphically.
• With object-oriented (OO) design, the programmer packages the data and the program into a single object
• Encapsulation
• The sequence control structure shows one or more actions following each other in order.
• The selection control structure tells the program which action to take, based on a certain condition.
• If then else
• Case
• The repetition control structure enables a program to perform one or more actions repeatedly as long as a certain condition is met.
• A program flowchart graphically shows the logic in a solution algorithm.
• Flowcharting software makes it easy to modify and update flowcharts
• SmartDraw
• Visio
• Pseudocode uses a condensed form of English to convey program logic.
• UML (Unified Modeling Language) has been adopted as a standard notation for object modeling and development.

Step 3 – Validate Design

• Check for logic errors using test data
• Develop various sets of test data
• Determine the expected result
• Step through the algorithm
• Compare the results
• Repeat steps for each set of test data

Step 4 – Implement Design

• Implementation of the design includes using a program development tool that assists the programmer by:
• Generating or providing some or all code
• Writing the code that translates the design into a computer program
• Creating the user interface
• Extreme programming is a strategy where programmers immediately begin coding and testing solutions as soon as requirements are defined.

Step 5 – Test Solution

• The goal of program testing is to ensure the program runs correctly and is error free.
• Errors include syntax errors and logic errors.
• Debugging the program involves removing the bugs.
• A beta is a program that has most or all of its features and functionality implemented.

Step 6 – Document Solution

• In documenting the solution, the programmer performs two activities:
• Review the program code
• Review all the documentation