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  • 简要辨析向下兼容、向上兼容、向前兼容、向后兼容四个概念之间的关联与联系。简言之,向上兼容等同于作向前兼容,向下兼容等同于向后兼容。主流使用的是向前兼容和向后兼容。向后兼容中“后”指“落后”,站新版本...

    摘要:

    简要辨析向下兼容、向上兼容、向前兼容、向后兼容四个概念之间的关联与联系。简言之,向上兼容等同于作向前兼容,向下兼容等同于向后兼容。主流使用的是向前兼容和向后兼容。向后兼容中“后”指“落后”,站在新版本的立场讨论过去版本的兼容性问题。向前兼容中“前”指“前进”,表示未来的事情,站在旧版本的立场讨论未来版本的兼容性问题。

    正文:

    向后兼容(Backward compatibility)

            Backward compatibility is the capability of interoperating with older systems. In telecommunications and computing, a product or technology is backward or downward compatible if it can work with input generated by an older product or technology. If products designed for the new standard can receive, read, view or play older standards or formats, then the product is said to be backward-compatible; examples of such a standard include data formats and communication protocols. The reverse is forward compatibility, which implies that old devices allow data formats generated by new devices, perhaps without supporting all new features. A standard supports forward compatibility if older product versions can receive, read, view, or play the new standard. For example, the introduction of FM stereo transmission allowed backward compatibility since new FM radio receivers could receive monaural signals generated by old transmitters. It also allowed forward compatibility, since old monaural FM radio receivers could still receive a signal from a new transmitter. In programming languages, backward compatibility refers to the ability of a compiler for version N of the language to accept programs or data that worked under version N - 1. By this definition, if previous versions were also backward compatible, which is often the case, then, by induction, version N will also accept input that worked under any prior version after, and including, the latest one that was not backward compatible. However, in practice, features are often deprecated and support is dropped in a later release, which is yet thought of as backward compatible.
            Backward compatibility is important because it eliminates the need to start over when you upgrade to a newer product. A backward-compatible word processor, for instance, allows you to edit documents created with a previous version of the program. In general, manufacturers try to keep all their products backward compatible. Sometimes, however, it is necessary to sacrifice backward compatibility to take advantage of a new technology.
            The flip side of backward compatibility is upward compatibility. Upward compatible is the same as backward compatible, except that it is from the point of view of the older model.
    向前兼容(Forward compatibility)
            Forward compatibility is the capability of interoperating with anticipated future systems. Forward compatibility aims at the ability of a design to gracefully accept input intended for later versions of itself. The concept can be applied to entire systems, electrical interfaces, telecommunication signals, data communication protocols, file formats, and computer programming languages. A standard supports forward compatibility if older product versions can receive, read, view, play or execute the new standard. The applicability of a forward compatible system with new versions requires not only the respecting of the older version by the designers of the newer version but additionally some agreement on future design features with the design freeze of current versions. The introduction of a forward compatible technology implies that old devices partly can understand data generated by new devices. 
    forward compatibility and extensibility:
            Although the concepts of forward compatibility and extensibility are similar, they are not the same. A forward compatible design can accept data from a future version of itself and pick out the "known" part of the data. An example is a text-only word processor ignoring picture data from a future version. An extensible design is one that can be upgraded to fully handle the new data in the newer input format. An example is a text-only word processor that can be upgraded to handle picture data.
            Forward compatibility is a design principle in which a program or piece of hardware is developed to remain functional in the future with new software or devices. For example, a computer program is typically written in code that allows it to work with an Operating System (OS) and hardware that is current at the time of its release. A developer creating a program with forward compatibility in mind tries to ensure that it will also be able to function several years later with a new OS and different hardware. This can be quite difficult to ensure, however, though certain methods can be used to make the process simpler.
    总结:
            向后兼容中“后”指“落后”,而不是“后来”,表示过去的事情,站在新版本的立场讨论过去版本的兼容性问题。向前兼容中“前”指“前进”,而不是“以前”,表示未来的事情,站在旧版本的立场讨论未来版本的兼容性问题。
            微软网站对“向后兼容”和“向前兼容”的理解:
          (1)向后兼容。2007 Microsoft Office 系统向后兼容下列早期版本:Microsoft Office 2000、Microsoft Office XP 和 Microsoft Office 2003。这些版本的用户可以轻松地采用新的格式,并继续从现有文件中获得最大的益处。特别是他们还可以继续使用旧的 .doc、.xls 和 .ppt 二进制格式,这些格式与 2007 文件格式完全兼容。
          (2)向前兼容。应用程序的早期版本能够打开较新版本中的文件并忽略早期版本中未实现的功能。例如,Word 2003 向前兼容 Word 2007,因为它能够成功地使用转换器打开 Word 2007 文件。

    向上兼容(Upward Compatible)
    向上兼容(Upward Compatible),又称作向前兼容(Foreward Compatibility)。在计算机中指在较低档计算机上编写的程序,可以在同一系列的较高档计算机上运行,或者在某一平台的较低版本环境中编写的程序可以在较高版本的环境中运行,都称为向上兼容,前者是硬件兼容,而后者是软件兼容。例如,基于Intel386的PC兼容机上所有的软件也可以运行在486或更高的机型上。向上兼容具有非常重要的意义,一些大型软件的开发,工作量极大,如这些软件都能做到兼容,则无需在其它机器上重新开发,就可节省庞大的人力和物力。

    向下兼容(Downward Compatible)
    向下兼容(Downward Compatibility),又称作向后兼容(Backward Compatibility)。在计算机中指在一个程序或者类库更新到较新的版本后,旧的版本程序创建的文档或系统仍能被正常操作或使用,或在旧版本的类库的基础上开发的程序仍能正常编译运行的情况。例如较高档的计算机或较高版本的软件平台可以运行较为低档计算机或早期的软件平台所开发的程序,如基于Pentium微处理器的PC兼容机可以运行早期在486上运行的全部软件。向下兼容可以使用户在进行软件或硬件升级时,厂商不必为新设备或新平台从头开始编制应用程序,以前的程序在新的环境中任然有效。
    对于软件来说,向下兼容的意思是,较高版本的程序能顺利处理较低版本程序的数据。拿著名的动画制作软件 Flash的两个版本 Flash 5(老版本)与 Flash MX 2004(新版本)来说,这两个版本虽然保存出来的文件都是 .fla,可是文件内容的结构有所不同。尽管如此,Flash MX 2004 仍然能处理 Flash 5 保存的 fla 文件,我们就说 Flash MX 2004 是向下兼容的。而Flash 5不能处理Flash MX 2004保存的fla文件,我们就说Flash 5不支持向上兼容。

    西安电子科技大学的《计算机体系结构》的考题答案中给出兼容性的定义:
    (1)向上(下)兼容指的是按某档机器编制的软件,不加修改就能运行于比它高(低)档的机器上。
    (2)向前(后)兼容指的是按某个时期投入市场的该型号机器上编制的软件,不加修改就能运行于比它前(后)投入市场的机器上。

    展开全文
  • 定义 此处先给出百度百科上的定义 向前兼容:是一个以较新版本编译的程序集是否可以较老版本上执行的问题。 向后兼容:是一个以较早...向下兼容(Downward Compatibility):又称向后兼容(Backwards Compatibil...

    定义

    此处先给出百度百科上的定义
    向前兼容:是一个以较新版本编译的程序集是否可以在较老版本上执行的问题。
    向后兼容:是一个以较早版本编译的程序集是否可以在较新版本上执行的问题。

    向上兼容(Upward Compatible):又称向前兼容(Forwards Compatibility)
    向下兼容(Downward Compatibility):又称向后兼容(Backwards Compatibility)

    记忆方法

    下面是我自己在看了一些博客之后的一些理解,便于记忆

    向前兼容:“前”指“前进”,所以当前版本是旧版本,讨论是否要兼容未来的新版本问题。Forwards Compatibility,Forward有“将来”的含义,所以是向将来兼容。
     
    向后兼容:“后”指“落后”,所以当前版本是新版本,讨论是否要兼容以前的旧版本问题。Backwards Compatibility,Backward有“回头”的含义,所以是向以前兼容。
     
    兼容:指的是兼容不同版本产生的数据集,当前版本是否应兼容前/后版本所产生的数据集。

    展开全文
  • 向下兼容、向上兼容、向前兼容、向后兼容四个概念之间的关联与联系: 向上兼容等同于作向前兼容,向下兼容等同于向后兼容。主流使用的是向前兼容和向后兼容。向后兼容中“后”指“落后”,站新版本的立场讨论过去...

    解析

    向下兼容、向上兼容、向前兼容、向后兼容四个概念之间的关联与联系:

    向上兼容等同于作向前兼容,向下兼容等同于向后兼容。主流使用的是向前兼容和向后兼容。向后兼容中“后”指“落后”,站在新版本的立场讨论过去版本的兼容性问题。向前兼容中“前”指“前进”,表示未来的事情,站在旧版本的立场讨论未来版本的兼容性问题。

    来源

    向后兼容(Backward compatibility)

    Backward compatibility is the capability of interoperating with older systems. In telecommunications and computing, a product or technology is backward or downward compatible if it can work with input generated by an older product or technology. If products designed for the new standard can receive, read, view or play older standards or formats, then the product is said to be backward-compatible; examples of such a standard include data formats and communication protocols. The reverse is forward compatibility, which implies that old devices allow data formats generated by new devices, perhaps without supporting all new features. A standard supports forward compatibility if older product versions can receive, read, view, or play the new standard. For example, the introduction of FM stereo transmission allowed backward compatibility since new FM radio receivers could receive monaural signals generated by old transmitters. It also allowed forward compatibility, since old monaural FM radio receivers could still receive a signal from a new transmitter. In programming languages, backward compatibility refers to the ability of a compiler for version N of the language to accept programs or data that worked under version N - 1. By this definition, if previous versions were also backward compatible, which is often the case, then, by induction, version N will also accept input that worked under any prior version after, and including, the latest one that was not backward compatible. However, in practice, features are often deprecated and support is dropped in a later release, which is yet thought of as backward compatible.
            Backward compatibility is important because it eliminates the need to start over when you upgrade to a newer product. A backward-compatible word processor, for instance, allows you to edit documents created with a previous version of the program. In general, manufacturers try to keep all their products backward compatible. Sometimes, however, it is necessary to sacrifice backward compatibility to take advantage of a new technology.
            The flip side of backward compatibility is upward compatibility. Upward compatible is the same as backward compatible, except that it is from the point of view of the older model.

    向前兼容(Forward compatibility)

            Forward compatibility is the capability of interoperating with anticipated future systems. Forward compatibility aims at the ability of a design to gracefully accept input intended for later versions of itself. The concept can be applied to entire systems, electrical interfaces, telecommunication signals, data communication protocols, file formats, and computer programming languages. A standard supports forward compatibility if older product versions can receive, read, view, play or execute the new standard. The applicability of a forward compatible system with new versions requires not only the respecting of the older version by the designers of the newer version but additionally some agreement on future design features with the design freeze of current versions. The introduction of a forward compatible technology implies that old devices partly can understand data generated by new devices.
    forward compatibility and extensibility:
            Although the concepts of forward compatibility and extensibility are similar, they are not the same. A forward compatible design can accept data from a future version of itself and pick out the "known" part of the data. An example is a text-only word processor ignoring picture data from a future version. An extensible design is one that can be upgraded to fully handle the new data in the newer input format. An example is a text-only word processor that can be upgraded to handle picture data.
            Forward compatibility is a design principle in which a program or piece of hardware is developed to remain functional in the future with new software or devices. For example, a computer program is typically written in code that allows it to work with an Operating System (OS) and hardware that is current at the time of its release. A developer creating a program with forward compatibility in mind tries to ensure that it will also be able to function several years later with a new OS and different hardware. This can be quite difficult to ensure, however, though certain methods can be used to make the process simpler.

    说明

    向后兼容中“后”指“落后”,而不是“后来”,表示过去的事情,站在新版本的立场讨论过去版本的兼容性问题。向前兼容中“前”指“前进”,而不是“以前”,表示未来的事情,站在旧版本的立场讨论未来版本的兼容性问题。
            微软网站对“向后兼容”和“向前兼容”的理解:
          (1)向后兼容。2007 Microsoft Office 系统向后兼容下列早期版本:Microsoft Office 2000、Microsoft Office XP 和 Microsoft Office 2003。这些版本的用户可以轻松地采用新的格式,并继续从现有文件中获得最大的益处。特别是他们还可以继续使用旧的 .doc、.xls 和 .ppt 二进制格式,这些格式与 2007 文件格式完全兼容。
          (2)向前兼容。应用程序的早期版本能够打开较新版本中的文件并忽略早期版本中未实现的功能。例如,Word 2003 向前兼容 Word 2007,因为它能够成功地使用转换器打开 Word 2007 文件。

    向上兼容(Upward Compatible)

    向上兼容(Upward Compatible),又称作向前兼容(Foreward Compatibility)。在计算机中指在较低档计算机上编写的程序,可以在同一系列的较高档计算机上运行,或者在某一平台的较低版本环境中编写的程序可以在较高版本的环境中运行,都称为向上兼容,前者是硬件兼容,而后者是软件兼容。例如,基于Intel386的PC兼容机上所有的软件也可以运行在486或更高的机型上。向上兼容具有非常重要的意义,一些大型软件的开发,工作量极大,如这些软件都能做到兼容,则无需在其它机器上重新开发,就可节省庞大的人力和物力。

    向下兼容(Downward Compatible)

    向下兼容(Downward Compatibility),又称作向后兼容(Backward Compatibility)。在计算机中指在一个程序或者类库更新到较新的版本后,旧的版本程序创建的文档或系统仍能被正常操作或使用,或在旧版本的类库的基础上开发的程序仍能正常编译运行的情况。例如较高档的计算机或较高版本的软件平台可以运行较为低档计算机或早期的软件平台所开发的程序,如基于Pentium微处理器的PC兼容机可以运行早期在486上运行的全部软件。向下兼容可以使用户在进行软件或硬件升级时,厂商不必为新设备或新平台从头开始编制应用程序,以前的程序在新的环境中任然有效。

    对于软件来说,向下兼容的意思是,较高版本的程序能顺利处理较低版本程序的数据。拿著名的动画制作软件 Flash的两个版本 Flash 5(老版本)与 Flash MX 2004(新版本)来说,这两个版本虽然保存出来的文件都是 .fla,可是文件内容的结构有所不同。尽管如此,Flash MX 2004 仍然能处理 Flash 5 保存的 fla 文件,我们就说 Flash MX 2004 是向下兼容的。而Flash 5不能处理Flash MX 2004保存的fla文件,我们就说Flash 5不支持向上兼容
     

     

     

     

     

     

     

     


     

    展开全文
  • 向上兼容与向下兼容

    千次阅读 2016-07-15 12:59:24
    或者某一平台的较低版本环境中编写的程序可以较高版本的环境中运行,都称为向上兼容,前者是硬件兼容,而后者是软件兼容,例如,基于Intel386的PC兼容机上所有的软件也可以运行486或更高的机型上。向上兼容...
    向上兼容   向上兼容(Upward Compatible)
      xiànɡ shànɡ jiān rónɡ
      在较低档计算机上编写的程序,可以在同一系列的较高档计算机上运行,或者在某一平台的较低版本环境中编写的程序可以在较高版本的环境中运行,都称为向上兼容,前者是硬件兼容,而后者是软件兼容,例如,基于Intel386的PC兼容机上所有的软件也可以运行在486或更高的机型上。向上兼容具有非常重要的意义,一些大型软件的开发,工作量极大,如这些软件都能做到兼容,则无需在其它机器上重新开发,就可节省庞大的人力和物力。
      向上兼容常常是相对于向下兼容而言的,两者在兼容的方向性上是相反的,因此这两个概念是不同的。

    向下兼容   向下兼容(Downward Compatible)
      又称 向后兼容(Backwards compatibility),计算机术语。
      对于软件来说,向下兼容的意思是,较高版本的程序能顺利处理较低版本程序的数据。拿著名的动画制作软件 Flash 的两个版本 Flash 5 与 Flash MX 2004 来说,这两个版本虽然保存出来的文件都是 .fla,可是文件内容的结构有所不同。尽管如此,Flash MX 2004 仍然能处理 Flash 5 保存的 fla 文件,我们就说 Flash MX 2004 是向下兼容的。
      但是由于考虑实际应用,不一定所有版本高的软件都能接受版本低的软件输出的东西,例如假设有一种软件 X,并假设现在已经有 10.0 版本了,那么版本旧得已经没有什么人用的 X 1.0 所输出的文件,就不太可能在 10.0 版本中顺利读取。

    展开全文
  • 向上兼容和向下兼容

    千次阅读 2015-07-23 14:32:13
    向上兼容和向下兼容其实可以是对同一事情两方面进行的不同描述而已。比如,我们针对JDK1.4平台开发的程序A能JDK1.5平台上进行正常运行,那么此时我们就说:程序A向上兼容JDK1.5平台,而JdK1.5平台向下兼容程序B...
  • JDK向下兼容问题

    千次阅读 2018-07-27 07:35:40
    1、jdk1.6 环境, JSP页面过大,访问报错, org.apache.jasper.JasperException: Unable to compile class for JSP: An error occurred at line: 158 in the generated java file The code of method _jsp...
  • 向上兼容于向下兼容

    千次阅读 2016-04-11 20:45:11
    计算机中指较低档计算机上编写的程序,可以同一系列的较高档计算机上运行,或者某一平台的较低版本环境中编写的程序可以较高版本的环境中运行,都称为向上兼容,前者是硬件兼容,而后者是软件兼容,例如,...
  • 向过去兼容 = backward compatibility (向后兼容, 回溯兼容) = downward compatibility (向下兼容) ,即现在设计的软件要考虑旧版本的数据还能不能用,比如开发Office 2007的时候,要考虑如何打开Office 2003的doc...
  • 关于Android 版本向下兼容

    千次阅读 2013-08-04 20:14:57
     N久未做android了,以前做的时候,2.2才刚出来,现在android都更新到了4.3了,而从前一段时间android各个sdk版本市场占有率 来看,1.6、2.1还是占有一定的市场,故有些时候,我们还是得要考虑兼容这些版本。...
  • win10 sdk 是否向下兼容

    千次阅读 2017-05-19 09:21:34
    我们安装了 sdk 为 14393 之后,选择项目工程为 14393 ,那么编译出来的程序可以win10 版本为红石之前的运行?
  • 什么叫向下兼容

    千次阅读 2014-06-25 21:41:51
    向后兼容(Backward Compatibility),又称作向下兼容(Downward Compatibility)。计算机中指一个程序或者类库更新到较新的版本后,用旧的版本程序创建的文档或系统仍能被正常操作或使用,或旧版本的类库的...
  • 向后(向下兼容

    千次阅读 2020-04-10 10:01:50
    这个疑惑我学习神经网络的时候解开了,神经网络中有前传播和后(反向)传播,其中前传播就是从输入层到输出层的代价函数计算,反向传播便是输出层到输入层的梯度计算方向如图所示: 所以,与前比起来,...
  • OpenCV版本向下兼容

    千次阅读 2015-12-21 10:50:01
    解决方法:项目属性里找到Linker->Input->Additinal Dependencies  把有关opencv的dll全部删掉,变成这样,让项目自动Inherit。 ps:如果直接把后缀改成300会有很多奇怪的error,直接删掉最方便。
  • jdk高版本向下兼容

    千次阅读 2019-11-13 21:05:58
    假设: 如果jdk是1.8的,但是需求是用1.7的来编译打包 方法如下: 右击项目->properties 选择Project Facets,如果右边是...选择java后面的Version 点击三角 选择1.7 最后apply就可以了 修改完毕 ...
  • 兼容
  • Android Material Design向下兼容至低版本Android SDK设备 新版的Android Material Design增加了一些很多有趣、有意思的设计元素和风格,比如最近比较常见的Floating Action Button等等。这新版的Android L,...
  • 开发环境:xcode4.6.3 SDK版本:IOS 6.1 ...如何让我的软件向下兼容那个而又不彻底重构代码的情况下,解决这个问题呢? 小弟我刚学IOS才一个月,希望各位大师指点迷津!不胜感激
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  • 一分钟理解兼容

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