I was using Turbo Pascal for about 20 years, but now I have changed my computer, and I have Windows 7 now. TP does not work under it. What similar language can I use instead of TP, that will require from me to spend minimum possible time studying it.
Turbo Pascal to Delphi (~ object oriented Pascal) would seem like the natural choice / progression.
Although a lot of other languages today are relatively easy to pick up as well (Python, Ruby, etc...).
I strongly advise you to learn C#.
You'll have to learn the OO Paradigma. But, once you get it, you'll enjoy the new world of modern computer programming.
Turbo Pascal evolved into Delphi, which is still used today but might be hard to find.
Your options are probably:
There is FreePascal:
It appears to be supported, I'm not sure how different it is to the Borland variant though.
Delphi is another option.
What kind of software do you expect to be able to write? Is this for professional development, hobby use,...?
If you are writing COTS software for Windows, I'd suggest one of the .NET languages. C# probably has the most publicly available tutorials, free code, controls, and such. Or learn Ruby and separate yourself from the crowd.
If you want to run the 20 year old Turbo Pascal on Win 7, you still can.
Download DosBox, and run TurboPascal in there. http://www.dosbox.com/
Python.
Cross platform, free, open source.
Has PyGTK, Tcl, wxWidgets and many more libraries for GUIs.
An application you write in Python will likely run well on all three main OSes (Windows, Linux, Mac) with little to no changes.
Python's syntax is similar to Pascal's but there are several important differences. For one, you don't define variables, and the types of variables are free to change. And there are no if ... then ... begin ... end statements as indentation is used.
It is also much more forgiving than Pascal syntax and type wise (not that that should be a reason for choosing a language!)
Because it is interpreted it will be slower. That can be a disadvantage for some applications, but it's usually not noticeable.
Yes, the natural progression would be to change to Lazarus/Freepascal or Delphi. I strongly agree that you can still run TP if you liked, though.
However, it is a very good opportunity for an update. C# is a programming language that was developed by the creator of Turbo Pascal/Delphi, and indeed it has many features borrowed from Object Pascal.
If you choose C# development of Mono, you can use very modern GUI such as Monodevelop and create multi-platform applications with GTK# without any effort.
http://www.mono-project.com/Main_Page
If you don't care about being multiplatform, you prefer to write software only for Windows, then you can choose Visual C# 2010 Express (its free):
FreePascal has a switch for TurboPascal compatibility (so you will have no need to change your programming habbits), and it can generate DOS, WIN32, WIN64 and other executables.