There are'nt any special pre-requisites to learn Pascal. Thus, you can start learning it straight away! Pascal is a very easy language, and helps beginners to introduce them to other languages, before they can start to learn C or C++ or any other advanced language (such as JAVA) - it is the doorstep to other high level programming languages .
Pascal is a high-level procedural programming language which is widely used as a beginner or as a teaching language. Sometimes Pascal is preferred to other languages, and could be useful to solve technical problems. It is not necessary to learn any other easier language to start learning Pascal, or any of that sort. It is a very easy programming language and helps you to understand the basics of the world of programming.
Also, it greatly helps you to start learning the C programming language. The Pascal programming language has its structure and syntax very similar to that of the C programming language. The successor language of Pascal is Delphi which is the object oriented version of Pascal.