APS审核—编程语言

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Programming Languages



1st Generation:Machine Language Operations in op-codes Operands

Numerical values Register number

Memory location address

2nd Generation: Assembly Language

A mnemonic system for representing programs Mnemonic: easy to remember More descriptive Enabling programming without tables such one in the Appendix C Things are mnemonic Op-codes in mnemonic names Registers in mnemonic names Memory locations in mnemonic names of the programmer’s choice (Identifiers)

3rd Generation Language Uses high-level primitives

Similar to our pseudocode in Chapter 5 Machine independent (mostly)

Each primitive corresponds to a short sequence of machine language instructions Converted to machine language by a program called compiler Examples: FORTRAN, COBOL, BASIC

Object-Oriented Paradigm

Grouping/classifying entities in the program Entities are the objects Groups are the classes Objects of a class share certain properties Properties are the variables or methods Encapsulation of data and procedures Lists come with sorting functions

Natural modular structure and program reuse Inheriting from mother class definitions

Many large-scale software systems are developed in the object oriented fashion

Objects and Classes Object Active program unit containing both data and procedures Class


A template for all objects of the same type An Object is often called an instance of the class.

Components of an object Instance variable Variable within an object Method Function or procedure within an object Can manipulate the object’s instance variables Constructor Special method to initialize a new object instance

Encapsulation A way of restricting access to the internal components of an object Private Public

Inheritance Allows new classes to be defined in terms of previously defined classes

Polymorphism Allows method calls to be interpreted by the object that receives the call

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