It depends on how the software is intended to work. A stand-alone system that is to be installed and operated on a PC could be written in Visual Basic or C++. A web based system that uses your browser to display static web pages could be written in HTML, a page formatting language. If it requires interaction with the user like this web site does, it would have to be scripted using a server side scripting language like perl script. The script would read the input from the user and redraw the pages in HTML.
That's a very brief description. There are many software products available to help automate the process. Generally, the easier the system is to learn, the more limitations on what you can do with it. If you want the maximum control over your project, the more complicated programming languages like the ones mentioned above offer that.
Answered Jul 27, 2010
Edited Jul 27, 2010