Whats the difference between Object Pascal and Delphi? Are they the same thing? What are the differences and similarities between them and which one is more useful?
Answer
Object Pascal was an object oriented extension of Pascal developed by Apple. The first version of Delphi was evolved from Turbo Pascal. The object oriented features in Turbo Pascal were, rightly, considered not fit for purpose. So Borland developed Delphi 1 and incorporated much of the Apple Object Pascal language. So the language for the Delphi product was originally named Object Pascal.
Apple stopped developing Object Pascal and it was never standardised as had been originally intended. For the release of Delphi 6, Borland chose to rename their language as Delphi.
You ask the question:
What's the difference between Object Pascal and Delphi?
But that's not really too meaningful since the original Object Pascal doesn't really exist in a distinct form any more. Apple abandoned it. The only extant implementations of Object Pascal like languages that are in widespread use are Delphi and the languages that it inspired: FreePascal, Oxygene, DWS, etc.
So a better question would be "What is the difference between Delphi and FreePascal?" Nowadays, Object Pascal is used loosely to refer to this family of related languages.