今天看到這篇文章，多了一些反思，其中文章所提的 “經常被情緒所左右” 這點最令我注意，恩，這確實是我該努力克服的方向。
很多人在做任何事情的時候，剛剛付出一點點，馬上就要得到回報。
但是我知道，放棄是一種習慣，一種典型失敗者的習慣。
你想獲得時間，你就得先付出時間，你想獲得金錢，你得先付出金錢。
成功者永不抱怨，抱怨者永不成功。
一個人成功與否，取決於五個因素：
（1）學會控制情緒
（2）健康的身體
（3）良好的人際關係
（4）時間管理
（5）財務管理
如果你想讓你的伙伴更加的優秀，很簡單，永遠的激勵和讚美他們。
其實建議的方式是最重要的，就是“三明治” 讚美，建議，再讚美！
當你讚美別人時候，你要大聲的說出來，
當你想批評別人的時候，一定要咬住你的舌頭！
一定要學習，一定要有一個空杯的心態。
你要永遠學習積極正面的東西，不看，不聽那些消極，負面的東西。
我們對於搜尋引擎過於誠實，你所留下的搜尋記錄，使得搜尋引擎比你的家人更了解你
其實沒有那麼生氣，那麼難過，只是不願接受這樣的自己而已。
真正的疙瘩仍是在於那不斷比較的心裡。
不願相信自己，也對自己沒有信心，即使知道自己其實沒有那麼差。
“這” 到底是不服輸的個性，還是單純旳嫉妒？
所謂的團隊應該是什麼樣子呢？
一直以來，我團隊的經驗似乎都不是很好。
不想造成他人的困擾，不，不是不想，是害怕。
即使如此，我不想輕易悲傷，因為我已經流太多眼淚了。
生活中得回覆各種期待，應付各種壓力。
有時就像工作一般，過多就令人討厭。
但我清楚這是我的人生，由我來決定，而我的人生不應該建築在不斷地追求。
我想告訴你，不要再競爭了，做自己就好，追求自己真正想要的東西 :)
單純，信念，展翅
2.1
The service and functions provided by an operating system can be divided into two main tags. Briefly describes the two tags and discuss how they differ.
Ans:
One class of services provided by an operating system is to enforce protection between different processes running concurrently in the system. Processes are allowed to access only those memory locations that are associated with their address spaces. Also, processes are not allowed to corrupt files associated with other users. A process is also not allowed to access devices directly without operating system intervention.
The second class of services provided by an operating system is to provide new functionality that is not supported directly by the underlying hardware. Virtual memory and file systems are two such examples of new services provided by an operating system.
2.2
Describe three general methods for passing parameters to the operating system.
Ans:
Register, Block, Stack
2.3
Describe how you could obtain a statistical profile of the amount of time spent by a program executing different sections of its code. Discuss the importance of obtaining such statistical profile.
Ans:
One could issue periodic timer interrupts and monitor what instructions or what sections of code are currently executing when the interrupts are delivered. A statistical profile of which pieces of code were active should be consistent with the time spent by the programin different sections of its code.
Once statistical profile has been obtained, the programmer couldoptimize those sections of code that are consuming more of the CPU resources.
http://wiki.answers.com/Q/Describe_how_you_could_obtain_a_statistical_profile_of_the_amount_of_time_spent_by_a_program_executing_different_sections_of_its_code?#slide=7
2.4
What are the five major activities of an operating system with regard to file management?
Ans:
The creation and deletion of files
The creation and deletion of directories
The support of primitives for manipulating files and directories （open, close, read, write, reposition）
The mapping of files onto secondary storage
The backup of files on stable (nonvolatile) storage media
2.5
What are the advantages and disadvantages of using the same system-call interface for manipulating both files and devices?
Ans:
Each device can be accessed as though it was a file in the filesystem. Since most of the kernel deals with devices through this file interface,it is relatively easy to add a new device driver by implementing the hardware-specific code to support this abstract file interface. Therefore,this benefits the development of both user program code, which can be written to access devices and files in the same manner, and device driver code, which can be written to support a well-defined API.
The disadvantage with using the same interface is that it might be difficult to capture the functionality of certain devices within the context of the file access API, thereby either resulting in a loss of functionality or a loss of performance. Some of this could be overcome by the use of ioctl operationthat provides a general purpose interface for processes to invokeoperations on devices.
http://quizlet.com/13315241/operating-systems-ch-2-flash-cards/
2.6
Would it be possible for the user to develop a new command intepreter using the system-call interface provided by the operating system
Ans:
Yes.
be able to develop a new command interpreter using the system-call interface provided by the operating system. The command interpreter allows an user to create and manage processes and also determine ways by which they communicate (such as through pipes and files). As all of this functionality could be accessed by an user-level program using the system calls, so it should be possible for the user to develop a new command-line interpreter.
2.7
What are the two models of interprocess communication? what are the strengths and weaknesses of the two approaches?
Ans:
One is message-passing model and the other is shared-memory model.
Message-passing strengths and weaknesses: message can be exchanged between the processes either directly or indirectly through a common mailbox. it is userful for exchanging smaller amounts of data and easier to implement for intercomputer communication. however,its speed is slower than shared-memory model.
Shared-memory strengths and weaknesses: it allows maxmum speed and convenience of communication. however,in the areas of protection and synchronization between the processes some problems exist.
2.8
Why is the separation of mechanism and policy desirable?
Ans:
The separation of mechanism and policy is important to provide flexibility to a system. If the interface between mechanism and policy is well defined, the change of policy may affect only a few parameters. On the other hand, if interface between these two is vague or not well defined, it might involve much deeper change to the system.
Mechanism and policy must be separate to ensure that systems are easy to modify.
http://wiki.answers.com/Q/Why_is_the_separation_of_mechanism_and_policy_desirable?#slide=6
http://ce.sharif.edu/courses/86-87/2/ce424/resources/root/Assignment%20Answers/OS-HW2%20Answers.pdf
2.9
It is sometimes difficult to achieve a layered approach if two components of the operating system are dependent on each other. Identify a scenario in which it is unclear how to layer two system components that require tight coupling of their functionalities.
Ans:
The virtual memory subsystem and the storage subsystem are typically tightly coupled and require careful design in a layered system due to the following interactions.
Many systems allow files to be mapped into the virtual memory space of an executing process. On the other hand, the virtual memory subsystem typically uses the storage system to provide the backing store for pages that do not currently reside in memory.
Also, updates to the file system are sometimes buffered in physical memory before it is flushed to disk, thereby requiring careful coordination of the usage of memory between the virtual memory subsystem and the file system.
https://www.google.com.tw/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC4QFjAB&url=http%3A%2F%2Fportal.unimap.edu.my%3A7778%2Fportal%2Fpage%2Fportal30%2FLecturer%2520Notes%2FKEJURUTERAAN_KOMPUTER%2FSemester%25202%2520Sidang%2520Akademik%252020102011%2FDKT%2520221%2520Operating%2520System%2520Principle%2FTutorials%2FAnswers%2FSolutions%25202.docx&ei=sTFNU532K5CtkgXimoCoCA&usg=AFQjCNECZ54D48gtLMQBxEcVF1Ot-b9PZQ
2.10
What are the main advantages of the microkernel approach to system design?
How do user programs and system services interact in a microkernel architecture?
What are the disadvantages of using the microkernel approach?
Ans:
Benefits typically include the following (a) adding a new service does not require modifying the kernel, (b) it is more secure as more operations are done in user mode than in kernel mode, and (c) a simpler kernel design and functionality typically results in a more reliable operating system.
User programs and system services could interact through message passing or shared memory .
the disadvantages is : suffer from performance decreases due to increased system function overhead (context switching increased).
http://wiki.answers.com/Q/What_are_the_disadvantages_of_a_microkernel?r2as=1#slide=2
http://answers-by-me.blogspot.tw/2010/11/operating-system-concepts-8e-exercise_8677.html
http://codex.cs.yale.edu/avi/os-book/OS8/os8j/practice-exer-dir/2-web.pdf
2.11
What are the advantages of using loadable kernel modules?
Ans:
Each is loadable as needed within the kernel with more flexible
2.12
How are iOS and Android similar, How are they different?
Ans:
the main similarities are: Android and iOS are both operating systems for mobile devices. They are both programmed in C and C++.
the differences are: Android is an open-source OS and iOS is a closed source OS.
ios is based on Mac OS X kernel.
android is based on Linux kernel.
http://wiki.answers.com/Q/How_are_iOS_and_Android_similar_How_are_they_different?#slide=5
2.13
Explain why java programs running on android systems do not use the standard java api and virtual machine?
Ans:
android api, Dalvik VM
2.14
Ans:(none)
