Self taught ADT and OOP

1、ADT

 Abstract Data Type, Abstract data types , It refers to the implementation of a data structure as a software component .ADT The interface of is defined by a type and a set of operations on that type , Each operation is defined by its inputs and outputs .

ADT It does not specify how the data type implements , These implementation details are important for ADT Is hidden from users , And through encapsulation （encapsulation） To prevent external access to him .

data structure （Data Structure） yes ADT The implementation of the , In such as c++ In object-oriented languages such as ,ADT And its implementation make up the class （class）. Same as ADT Each operation that is linked together is represented by a member function （member function） To achieve . Data structure refers to the data stored in the computer memory , File structure refers to the organization of data in external storage .

For using the same ADT Two applications , There may be an application that uses ADT The case where there are more special methods than the other or where these two procedures are applicable to the ADT The operation of has different time requirements . It is because of the differences in the requirements of the application , To make a given ADT There are many possibilities for implementation .

problem ： Intuitively , The problem is nothing more than a task to be completed , That is, a group of inputs has a group of corresponding outputs .

Algorithm ： An algorithm is a method or process of solving a problem .

Program ： A computer program is considered to be a concrete implementation of an algorithm using a programming language .

2、OOP

OOP：oop It's object-oriented programming , Object oriented programming is a kind of computer programming architecture ,OOP One of the basic principles is that a computer program is composed of a single unit or object that can play the role of a subprogram .

OOP characteristic ：

1、 encapsulation ： Also known as information hiding , That is to separate the use and implementation of a class , Only some interfaces and methods are kept in contact with the outside world , In other words, only some methods for developers are disclosed . So developers just You need to pay attention to how this class is used , Instead of caring about the specific implementation process , In this way... Can be achieved MVC work in cooperation with a due division of labour , It can also effectively avoid interdependence between programs , Realize loose coupling between code modules .
 2、 inheritance ： That is, a subclass automatically inherits the properties and methods of its parent class , And you can add new properties and methods or rewrite some properties and methods . Inheritance increases the reusability of code .PHP Only single inheritance is supported , That is to say, a subclass can only have one parent class .
 3、 polymorphism ： Subclasses inherit properties and methods from the parent class , And rewrite some of the methods . So although there is the same method in many subclasses , But the objects instantiated by these subclasses can get completely different results by calling these same methods , This technique is polymorphism . Polymorphism enhances the flexibility of software .

Use OOP The benefits of ： 

1、 Easy maintenance
  Structure designed with object-oriented idea , High readability , Because of inheritance , Even if demand changes , Then maintenance is only in local modules , So maintenance is very convenient and low cost .
 2、 High quality
  In design , Reuse existing , The classes that have been tested in previous projects make the system meet business requirements and have high quality .
 3、 Efficient
  In software development , Abstract things in the real world according to the needs of design , Production class . Use this method to solve problems , Close to everyday life and natural way of thinking , It is bound to improve the efficiency and quality of software development .
 4、 Easy to expand
  By inheritance 、 encapsulation 、 Polymorphism , Naturally designed to be highly cohesive 、 Low coupling system structure , Make the system more flexible 、 It's easier to expand , And it costs less .