Programs and Data

Object-oriented programming is a popular way  of managing programs, which  groups together data  with  the procedures that  works on them,  thus  facilitating some  types  of abstraction and modularity.  In the case  of our  PCAP  framework, object-oriented programming can provides us methods for capturing common patterns in data and the procedures that operate on that data, via procedures, generic  class, and inheritance.

In many  computer languages, adding Python, programs are  studied and  executed by a computer program known as  an interpreter. Interpreters are surprisingly easy:  the principle  de?ning the semantics or meaning of a programming language are typically short and compact;  and the in­ terpreter basically  encodes these rules and applies them to any legal expression in the language. The enormous complexity and  richness of computer programs comes  from  the  composition of primitive elements with  simple  principle.   The interpreter, in essence,  shows the  semantics of the language by taking the rules  governing the value  or behavior of program primitives, and  of what  it seems to collide the primitives in various paths.  We will examine the meaning of computer programs by understanding how the interpreter operates on them.

An interpreter is build  up of four sections:

• The reader or tokenizer takes as input a string of characters and divides them into tokens, which are numbers (like -3.42), words (like while or a), and special characters (like :).

• The parser gets as input the string of tokens and understands them as constructs in the programming language, such as for loops, procedure de?nitions, or return variable.

• The evaluator (which is also sometimes called the interpreter, as well) has the really interesting job of determining the value and effects of the program that you ask it to interpret.

• The printer gets the value given by the evaluator and prints it out for the user to see.

Programs should never  be a mystery to you:  you can learn  the simple  semantic rules  of the language  and, if compulsory, examine what  the interpreter would do, in order  to study any computer code which  you are acting.  Of course,  in general, one does  not has  to work  through the tedious procedure  of simulating the interpreter, but this foundation of calculating the interpreter 's process  enables  you to reason  about  the evaluation of any program. #question..