Linux I/O(二) : A Process Of Reading Disk File

July 14th, 2016 No comments

What’s IO?

IO(Input/Output) is a system of communication for information processing systems.

In computing, IO is the communication between an information processing system , such as a computer, and the outside world, possibly a human or another information processing systems, such as keyboards and mouse are input-only devices while devices such as printers are output-only. A writable CD-ROM is both an input and an output device. IO is a system of communication,structure of IO system in linux,as follows:

archetectureofkernelio

由上图可看出,设备驱动充当“翻译官”角色,承担操作系统与设备之间沟通,不同设备对应不同的设备驱动。

linux IO系统,向下:通过安装设备驱动,横向扩展可访问设备种类;向上:通过封装统一访问入口,降低上层应用访问各设备的复杂度。

由此看来,IO子系统在linux操作系统中扮演“承上启下”角色。如果,我们把操作系统比喻成计算机的心脏,那么IO系统则是血管,没了它,计算机就是一潭死水。下面以设备disk为例,介绍计算机和设备之间如何进行IO交流。

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Use Case Description Template

April 26th, 2016 No comments

日常工作中, 看惯千奇百怪的用例的文档,十分随意,充其量是个人意淫的功能点测试,不具备Use Case的场景化。提供如下的Use Case模板,仅供参考:

啃需求,捋Case

编写Use Case description前,建议先啃需求,捋Case

make a reservation22

根据“二八定律”,系统关键功能占20%,写好这20%的use case,则会覆盖系统80%的测试功能点。

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歌词摘录《空谷幽兰》

January 29th, 2016 No comments

《空谷幽兰》

—许巍 《此时此刻》专辑

纵有红颜 百生千劫

难消君心 万古情愁

青峰之巅 山外之山

晚霞寂照 星夜无眠

如幻大千 惊鸿一瞥

一曲终了 悲欣交集

夕阳之间 天外之天

梅花清幽 独立春寒

红尘中 你的无上清凉

寂静光明 默默照耀世界

行如风 如君一骑绝尘

空谷绝响 至今谁在倾听

一念净心 花开遍世界

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Key In Http Protocol (一): ‘Cache-Control’

January 28th, 2016 No comments

Brief Background

HTTP (Hypertext Transfer Protocol) is perhaps the most popular application protocol used in the Internet (or The WEB).

HTTP is an asymmetric request-response client-server protocol as illustrated.  An HTTP client sends a request message to an HTTP server.  The server, in turn, returns a response message.

In other words, HTTP is a pull protocol, the client pulls information from the server (instead of server pushes information down to the client).

HTTP is a client-server application-level protocol.

HTTP

¶ http response message

HTTP_ResponseMessageExample

¶ http request message

HTTP_RequestMessageExample

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Categories: protocol, web Tags:
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