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Most programming languages were designed back in the days when computer screens displayed nothing but text. The screen didn’t show graphics, mouse pointers, buttons, or windows.

Because computer screens could display only text, languages such as C++, BASIC, and Pascal had simple commands to display information, such as the following BASIC command:

PRINT “This sentence appears on-screen.”

After computers developed fancy graphical user interfaces with windows, scroll bars, and toolbars, people began demanding programs that included all these fancy graphical features. To help programmers create programs with graphical user interfaces, many companies developed special dialects of existing languages, which they dubbed rapid application development (RAD) languages.

RAD languages enable programmers to design the way that they want their programs to look (the user interface) and then write source code to make that user interface actually do something useful, such as display information in a window. 

Some popular RAD languages are Visual Basic and REALbasic (based on BASIC), Delphi and Kylix (based on Pascal), and Visual C# (based on C#).

RAD languages offer the following benefits:

•  Speedy writing: You can write programs with graphical user interfaces much faster by using RAD than you can by using ordinary C++, BASIC, or Pascal. 

•  Less work: 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.

•  Similarity to other languages: Because RAD languages derive from existing high-level languages (BASIC and Pascal), you can learn and start programming in a RAD language right away if you already know 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:

•  Low portability: Programs that you write in RAD languages may not be portable between different computers. Delphi and Kylix can only create programs that run on Microsoft Windows and Linux, but can never create programs that run on the Macintosh without extensive modification. (Early versions of both Visual Basic and Visual C# also created programs that could only run on Windows, but newer versions promise to run on other operating systems as well. However, note the word “promise.” If you need to create a program that runs on Windows, Linux, and Mac OS X right now, a “promise” for tomorrow isn’t going to help you today.)

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

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