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RAD languages simplify the process of creating user interfaces so that you can focus on getting the rest of your program to work. Without a RAD language, you’d need to write instructions to make the user interface work and then write additional instructions to make the rest of the program work as well, essentially doubling your work and the chance of making a mistake.

Because RAD languages derive from existing high-level languages (C++, BASIC, and Pascal), you can learn and start programming in a RAD language right away if you already know C++, BASIC, or Pascal.

Not surprisingly, RAD languages have a few major drawbacks, which shouldn’t surprise you because nothing involving computers is ever perfect. The following list describes these drawbacks:

Programs that you write in RAD languages are rarely portable between different computers. Visual Basic runs only on Microsoft Windows 98/Me/NT/2000/XP, for example, so if you write a program in Visual Basic, you can never run it on a Macintosh, Linux, or other computer operating system without extensive modification.

RAD languages create larger and slower programs than the equivalent programs written in pure C++, BASIC, or Pascal. A RAD language may help you create programs faster, but you sacrifice speed and program size.

Database programming languages

Programming languages such as C++, BASIC, and Pascal were designed as general-purpose languages, which means that you can use them to write a flight simulator, an accounting program, a voice-recognition program, or a word processor.

One of the most popular uses for computers, however, is storing and retrieving information, such as names, addresses, phone numbers, prison records, credit history, and past job experience. Computers store such information in a database.

Almost every business relies on databases to store information about customers, inventories, and employees, so nearly every company uses a database program.

Unfortunately, most people don’t want to know the strange and often bizarre commands necessary to store, retrieve, or print information from a database. To make databases easier to use, most databases include a programming language.

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If you write programs using a database’s programming language, you can create custom databases for different companies. Best of all, database programming languages enable you to create custom databases much faster than using a general-purpose language such as C++ or BASIC. If you use a database programming language, you write instructions only to manipulate the database information. If you use a general-purpose language such as C++, you must write instructions to store information and then write additional instructions to manipulate that information, essentially doubling the

amount of work to accomplish the same task.

Most popular database programs, such as FileMaker and Microsoft Access, offer their own special programming language. For manipulating large amounts of data such as on big mainframe computers, database programs tend to use a language known as SQL (which stands for Structured Query Language). The following SQL code displays the message “Take a nap!”

select ‘Take a nap!’ from dual;

Database programming languages can fill the following specific needs:

If you’re writing a program that stores huge chunks of information, you can write a program much faster by using a database programming language than by using a general-purpose language such as C++ or Pascal.

Database programming is a lucrative field. If you know how to create customized databases, you almost never need to worry about being unemployed or not making enough money.

Of course, database programming languages aren’t for everybody. They have several crucial limitations, as the following list describes:

Database programs are often tied to a specific computer. If you write a custom database using FileMaker, for example, you can run your program only on a computer that can also run the FileMaker program. Because FileMaker is currently limited to the Macintosh and Windows operating systems, you can’t run a FileMaker program on a computer that uses Linux.

Database programming languages are great at making custom databases but lousy at making anything else, such as video games, word processors, or utility programs (such as anti-virus utilities). If you need to create a variety of programs, you can’t rely on a database programming language by itself.

Scripting programming languages

Writing a program from scratch gives you the most flexibility but can take a really long time and drive you nuts in the process. Suppose, for example, that you want to write a word processor specifically for creating screenplays.

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If you decide to use a general-purpose language such as C++ or Pascal, you first need to write instructions that create a simple word processor; you then need to write additional instructions to give the word processor the features necessary to create and format screenplays.

As an alternative to going mad by writing everything yourself, many programs offer their own scripting languages. Rather than write an entire word processor from scratch, you can buy an existing word processor (such as WordPerfect or Microsoft Word) and then use that word processor’s scripting language to make the word processor do what you want it to do (such as create and format screenplays). A scripting language enables you to focus on the task that you want to accomplish without worrying about irrelevant details.

Most Microsoft programs, such as Word, Excel, PowerPoint, and Access, offer a scripting language known as Visual Basic for Applications (VBA), which is nearly identical to Visual Basic. The Macintosh operating system also includes a scripting language, known as AppleScript, so you can write programs to automate your Mac (to a limited extent). The following code shows how to use AppleScript to display the message, “Take a nap!” on-screen:

on DisplayMessage()

display dialog “Take a nap!” buttons {“OK”}

end DisplayMessage DisplayMessage()

Scripting programming languages can come in handy in many of the following ways:

A scripting language enables you to modify an existing program, such as a word processor or spreadsheet. That way, you can create sophisticated programs quickly with very little programming.

Scripting languages are generally easier to learn than more powerful programming languages, such as C++. As a result, you can learn and start writing programs faster.

But before you jump wholeheartedly into learning and using a scripting language, beware of the following problems:

Scripting languages are tied to a specific program. If you customize a word processor by using a scripting language, your program runs

only on computers that run that particular word processor. If you customize Microsoft Word, your program works only on computers that can run Microsoft Word, such as Windows and Macintosh computers.

Selling and distributing your programs is much more difficult. To use your program, people must buy or already own the program (word processor, spreadsheet, and so on) that you customize. So if you create a custom program for WordPerfect, Microsoft Word users can’t use it.

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A scripting language provides much less flexibility than does a generalpurpose programming language such as C++. Make sure that the tradeoff of convenience and ease of programming is worth the limitations of using a scripting language.

Web-page programming languages

In the early days of the Internet, people communicated through plain old text without fancy graphics, animation, or forms that make up today’s Web pages. Although people have been reading text for years, it can get boring and difficult to read if you view it on a computer screen that requires constant scrolling to view an entire document.

To remedy this problem and spruce up the appearance of text, programmers created HyperText Markup Language (HTML), which defines the graphical appearance of Web pages. Figure 2-3 shows a typical Web page as its HTML code defines it.

HTML codes tell a browser how to display a page. So whenever you use a browser to view a Web page (such as www.dummies.com), your browser

automatically converts the HTML code into the fancy graphics, as shown in Figure 2-4.

Figure 2-3:

HTML code can look messy and unreadable.

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Figure 2-4:

The cryptic HTML code from Figure 2-3 actually defines the appearance

of the For Dummies Web site.

After a while, people got tired of plain ol’ HTML Web pages that resemble billboards that you view through your computer screen. To make Web pages capable of interacting with the user (for playing games, filling out forms, and so on), programmers created special Web-page programming languages such as Java, JavaScript, and VBScript.

Java can create two types of programs: stand-alone applications (such as games or word processors) and smaller applets, which can run off a Web page. The following code shows how a Java application can display the words, “Take a nap!” on-screen:

public class DisplayMessage {

public static void main (String args[]) { system.out.println (“Take a nap!”);

}

}

Web-page programming languages enable you to create Web sites that more closely resemble video games than scanned images of paper on a computer screen. Such interactive Web pages can increase interest in your Web site and encourage people to return.

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Web-page programming languages offer the following advantages:

You can create interactive Web pages to make your site more interesting to look at and to encourage viewers to stay on your site longer.

The language is easy to learn and enables you to create programs that anyone around the world with Internet access can use.

Then again, Web page programming languages are very limited in their capabilities, as the following list describes:

Not all browsers support all features of Web page languages such as JavaScript or VBScript. As a result, users of older browsers can’t run programs that you create by using Web-page languages.

For Internet users saddled with slow access (such as through a 28.8 baud modem), programs that you create in a Web-page language (such as VBScript) can run slowly, discouraging visitors from visiting your Web site.

Only people with Internet access can run programs that you create with a Web-page language (except for Java). If you want to sell a program to others, you don’t want to use a Web-page language.

So What’s the Best Programming Language to Learn?

No single “best” programming language exists. If you want to write programs professionally, you want to learn at least one high-level language (most likely C++ because it’s currently the most popular of the high-level languages) and one database programming language (such as SQL). You can’t go wrong learning C++. With so many companies writing programs in C++, people with C++ programming experience can get a job almost anywhere.

But the immense popularity of C++ programming means that competition is often high. Because thousands of older computers still run COBOL programs that need constant updating, many programmers are finding a lucra-

tive career learning to write and modify COBOL programs. With fewer COBOL programmers available, companies often must pay COBOL programmers a higher salary.

For those planning to work for themselves, one of the most lucrative markets is writing custom databases for other companies. To get into this field, you obviously must know a database programming language, such as SQL or VBA, which Microsoft Access uses. If you plan to create Web pages, you need to know HTML and gain some familiarity with Java, JavaScript, VBScript, and

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the other Internet programming languages. Ultimately, the best programming language to know is the one that enables you to accomplish the task that you want as quickly and easily as possible, whether that language is C++, BASIC, Java, SQL, or assembly language.

For a quick introduction to the way different programming languages solve the same problem, visit the Hello World! Web site at www.latech.edu/~acm/ HelloWorld.shtml. This Web site provides sample programs, written in a variety of programming languages, which tell the computer to display the words “Hello World!” on-screen.

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Chapter 3

How to Write a Program

In This Chapter

Designing your program

Understanding the technical details

Choosing a programming language

Defining how the program should work

Knowing the life cycle of a typical program

Although you can sit down at your computer and start writing a program right now without any planning whatsoever, the result would likely to

prove as messy as trying to bake a cake by throwing all the ingredients together without following a recipe.

You can write a simple program that displays your cat’s name on-screen without much planning, but for anything more complex, you want to take time to design your program on paper before you even touch a computer. After you’re sure that you know what you want your program to do and how you want it to look on-screen, you can worry about writing a program that actually accomplishes this task.

Before You Write Your Program

If you design your program before writing it, you don’t waste time writing a program that doesn’t work or that solves the wrong problem and isn’t worth trying to salvage afterward. By planning ahead of time, you increase the odds that your program actually works and performs the task that you want.

The following three items are crucial to consider in designing a program:

The user: Who’s going to use your program?

The target computer: Which computer do people need to run your program? Is it a Windows 98/Me/NT/2000/XP computer, a Macintosh, a mainframe, a computer running Linux, a handheld Palm or PocketPC, or a supercomputer?