When you ask this question: ‘What were the principles based on which the programming language was developed?’ It kind of points out to the paradigms. Yes, It is essential to know about programming paradigms. They tell us the motivational story behind the language. They tell us how the language has perceived the real world. They tell us how a language models the real world scenarios. The short description added below will sure help:
Imperative is a procedural programming. The change of states of a program is observed incrementally with respect to function of time. Various control structures govern the execution of the program statements. Few examples of languages which fall under this category are C, FORTRAN, ALGOL, Pascal etc.
Functional originates from mathematics. Here time plays a minor role and the languages are about expressing the statements of a program in a formal way. The languages stress on the evaluation and using the resulting value. Examples of languages that fall under this category are Haskell, Scheme, Erlang etc.
Logical refers to languages built on axioms, inference rules and queries. To name it more aptly in today’s context, its artificial intelligence. Prolog, Datalog etc are examples of languages that fall under this category.
Yet another paradigm is Object oriented. It models the human interaction with real world phenomenon using the concept of objects. Objects communicate with each other by passing the messages. C++, C#, Java etc are examples of languages that fall under this category.