Wednesday, October 20, 2010

What is the JPEG2000

Analysis: Chao-phase

Full name JPEG Joint Photographic Experts Group, it is a International Standards Organization (ISO) engaged in a static image compression standard developed by the Commission. It worked out the first set of national standard still image compression standard: ISO 10918-1 JPEG is what we called a. As the JPEG fine quality, making it in just a few years and great success, the current site on 80% of the image is compressed using JPEG standard. However, with the proliferation of multimedia applications, the traditional JPEG compression technology has been unable to satisfy the requirements of the multimedia image data. Therefore, a higher compression ratio and more new features of next-generation JPEG 2000 still image compression technology was born.

JPEG 2000 is formally known as "ISO 15444", the same organization responsible for the development by the JPEG. Since March 1997 the planning, but a few years, the issue of delay in the algorithm selected a lot of time, it is widely expected to go to in December 2000 to develop JPEG2000 was completed in March 2000 at a meeting in Tokyo may be due to digital camera manufacturers put pressure on the final provisions of the basic coding system introduced earlier draft agreement was finally renamed as JPEG2001 without a.

JPEG2000 principle:

JPEG JPEG 2000 and the biggest difference between traditional, in that it abandoned the JPEG discrete used to convert the remaining string (Discrete Cosine Transform) block-based encoding, and used the wavelet transform (Wavelet transform)-based multi-resolution encoding. The main objective of wavelet transform to the image of the frequency components extracted. Simple diagram can refer to the diagram.

JPEG2000 advantages:

1, JPEG2000 upgrade as JPEG, high compression (low bit rate) is the goal, the JPEG compression ratio higher than about 30%.

2, JPEG2000 supports both lossy and lossless compression, while JPEG only supports lossy compression. Save it for important pictures.

3, JPEG2000 can achieve progressive transmission of JPEG2000 this is an extremely important feature. This is the GIF format images we often say "Starts" feature. It is the first outline of image transmission, and then gradually transfer the data to continuously improve image quality, so that images from the obscure to the clear display, but not necessarily the same as the current JPEG, shown from top to bottom slowly.

4, JPEG2000 support the so-called "region of interest" feature, you can specify the image you are interested in any area of the compression quality can also choose to specify some of the first extract. So that we can easily highlight the point.

JPEG2000 applications:

JPEG 2000 application areas could be roughly divided into two parts, a market for traditional JPEG, such as printers, scanners, digital cameras, etc.; an emerging application areas, such as network network transmission, wireless communications, medical images. The current enthusiasm for JPEG 2000 is the biggest digital camera maker that. JPEG JPEG 2000 and the obvious advantages compared to, and backwards compatibility, just around the corner to replace the traditional JPEG format.

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Monday, October 11, 2010

How I sold 1,000 cars, 200 sets of villas

It is said that the Chinese real estate tycoon, Pan Shiyi, the richest man is out from the countryside. I was out in rural areas, in the eyes of the old generational, rural people can be soldiers, that's pretty good, if the regularization of the energy officials, and the whole village would turn all the boiling, I think so.

But since I know Pan Shiyi, who is also the rural areas, he became the object of study in my heart, I know that rural people could be turned into Pan Shiyi.

I read that the University of International Trade, after graduation, in a second tier cities to find work. This work is in the local computer market stalls selling computer accessories. Could get more than 800 pieces a month, my first month's wages when the hand, heart felt extremely happy, I feel I am a city person, and I earn more than those who are home more. In this way, done a year or so, I think, should not seek greater development of some, after all, the time has come to get married, I need more money.

So I went to a car shop 4S candidates. During that time, simply run into a wall every day, almost all of the 4S shops are not giving me the opportunity, the general reason is that Mandarin is poor, the overall quality does not meet the requirements, poor personal image and so on. After several twists and turns, or a manager, my fancy will power, accept me, then that I embarked on a road vehicle sales.

Before the day playing with computer hardware, application software really know nothing about. The 4S shop called with a set of CRM software, the manager said to help increase sales. I am skeptical, a software company can make more money? The first time I heard such wonderful things, impressed, this software is called Odin CRM, is developed in Wuhan.

Just two weeks to work, the company gave me training, I also worked hard at learning the knowledge of vehicle sales. After the training, I am smooth as Mr. cars and embarked on work. At first, the sales work is not very smooth, I pains 2 months may not be able to sell one. Manager, a conversation with me, let me Fa Xian of the Zishen many problems, for example Shui Mouge customer Yi Qian came, Bingjutianxie a customer information card, the next he Zai came in, I could not remember this person is not to too. I feel like I have asked the manager what capacity should be increased, I simply do not come out of. Finally, he asked me a question, you provide the CRM with useless software ah? I said: never opened, what the thing can use. Followed by a manager, right about face in the lecture, told me that if you no longer need, then do not come to work next month!

I own all of the collected customer information card to fill all in the system. As long as there is free time, I see over and over again the information through the system provides some of the features of which customers are likely to buy a car, which is not possible. Then according to these results, for different customers into different energy. System, which the man called to do "sales funnel analysis" tool, through this function, I learned that he put into the basis of invalid customer's ability to very poor customers. For its own question, I have carried out a series of learning and effort.

This way, after 1 year, the statistics so I was startled - I sold a 1002 car! I did it! At the same time, I also have a new goal - real estate. After all, what car is only a few hundred thousand, a house which millions, tens of millions of it.

I came to Beijing, applicants to a real estate company, started my career in real estate sales. In my suggestion, also purchased a set of CRM software. Now I have a wife have children, have their own house, own car. Grateful that the software company, Wuhan, let me know CRM, thank them for helping me find the road to success.

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Monday, September 27, 2010

Direct Marketing Manager: your direct sales beyond

With the external environment, the gradual recognition of the direct marketing, more and more companies concerned about the direct sales of this model, even in transition to direct selling companies, which promote the direct selling industry demand for qualified personnel increased sharply. Particularly good direct marketing manager, worth more than a million. And traditions of different professional managers, direct sales manager good is gravely deficient. Meanwhile, the direct selling enterprises and direct trust between the manager, but is also considered very low.

Direct marketing manager "original"

So, the current environment, the domestic direct selling what are types of managers? Through the analysis of the entire direct marketing environment, we can easily find the current domestic direct sales managers are mainly the following types:

1, from foreign well-known direct selling company executives, such as Amway, Avon and other cross-border direct marketing giants. From overseas, with a high degree; years of direct senior management experience; years, large multinational companies to help develop the Chinese market has accumulated a large number of personnel resources, especially good government relations; annual salary is generally a million; these are such direct marketing manager's characteristics and advantages.

2, by the successful transition from the direct dealer manager. And the first direct comparison managers, such managers from being subjected to Jiaoyuchengdu, overall quality, management experience, teamwork Neng Li, long-term strategic planning and thinking and Du obviously Chuyuruoshi, Dan more familiar marketing Huan Jing, Bentu combat experience rich, can be grouped into "guerrilla" Legion.

3, from the traditional industry executives to switch from the manager. These people have the wealth manager, management experience, and Zhang Qi direct attention to development of the industry, focus on corporate strategy for long-term planning, but lack direct selling industry combat experience made them Chuli degree from the things Lai Po Xian flexible enough to reflect insensitive, requiring a longer adaptation period.

4, who is the boss (investor) and the direct manager of the identity of the person. This type has divided into two, if the owner is very familiar with the direct selling industry, would be more in the operating smoothly, otherwise, is cautious, need to charge a number of twists and turns.

Several types of direct marketing over the manager direct sales companies throughout China, but actually in the business environment play an important role, leading direct selling companies to "nirvana" and trivial. In the management process is not overly dependent on direct sales of this model while ignoring corporate strategy, corporate culture and institution-building, direct sales company that is unable to communicate with the owner of a virtuous policy consensus which led to waving. Since the industry's first burst House Industry Co., Ltd. Shenzhen Neptunus Neptune Health House Fan Yu Lin CEO since he took office 88 days after the sudden resignation, direct marketing manager jobs frequently news constantly, which strongly impact on the image of direct marketing manager, direct sales manager the quality of the gradual often criticized by outsiders.

The quality of direct managers fault, and domestic business schools in the absence of direct selling is not unconnected, and the direct manager also impetuous, arrogant attitude and poor compression and quality issues are closely linked.

In the United States, South Korea, Japan, the direct sales market has been very mature in their country's business school marketing professional, and at least there will be more than 20 hours is to teach the content of direct learning, but no major business school in the country notes this field blank in the business of teaching. This lack of education caused most of the domestic direct sales manager out of the market line Mang Fu hustle, lack of a systematic discipline based on knowledge and experience in analysis and synthesis, so that these direct sales staff in the process towards direct marketing manager , the difficult to break through concepts, ideas on the bottleneck, and thus can not be a good understanding of corporate strategy and culture. And frequently change jobs, vanity role, together with immature external environment in which a number of direct sales manager insurmountable emotional disorders, and thus stopped.

How to go beyond direct sales direct sales manager?

With the trend of direct selling market Zhubu mature, distributors Yeyuelaiyue Li Xing, they Zhu Jian Mingbaichuantong Xiaoshouqiye and direct selling companies in addition to marketing Moshi Butongyiwai, more so in corporate culture, system, mechanism there exist considerable differences and conflicts between . Enterprises to withstand the turbulent market economy, in the brutal competition in the most populous, need more advanced and scientific management experience and system to boot. This determines the quality of management is more important to them. From the development trend, the company's management than the quality of direct understanding of the industry is more important. So, making the best direct marketing manager, standard gradually appear, there is no doubt that this will promote the growth of a number of direct sales professionals to find the direction, and gradually enrich the direct marketing industry, the team manager.

So, what kind of professional managers in the end the best talent is now direct the development of enterprises? We can start with related media named the 2006 top ten direct marketing manager to a small glimpse of the overall quality of clues. Top Ten success of the relevant agencies who covers multinational direct sales manager, direct sales company in China for direct selling business people and local executives, most leading companies in related industries to which the performance of non-Fei. Ten successful professional managers, although managers in different, different personality, distinctive style of management, but basically possesses the design or the firm's strategy deep Lijienengli; are deep plowing in the corporate culture of the construction and dynamic enterprise mechanism upgrade; are engaged in direct selling industry for many years and to control a strong network of resources.

Thus, direct marketing is only a model, direct marketing company first and foremost a business, the company's management can not do without the correct interpretation of corporate strategy and improve the corporate culture. Direct managers first need to get out "eyes only for direct sales," the error, the correct attitude to look at the development of a direct selling business and management issues. A certain scale of traditional direct sales experience in the company's executive manager, know how to understand how the business development strategy through effective implementation of the terminal in the management of cash as profit. With the quality manager can get along better with business owners and business owners exploiting the boundary with the way singing. From the top ten success in direct sales manager's evaluation is not difficult to find, and business owners have a consensus on the strategic depth of operations is to obtain a high degree of trust and move towards success.

Secondly, practitioners have had direct experience or direct sales industry model can accurately interpret, and accumulated the required business connections, direct sales manager is a very important one of professional quality. Familiar with the operation of direct selling model, with extensive experience in direct sales, direct sales force to promote market development team to overcome the problems encountered during the process, through effective skills training, incentives, build a strong direct sales team to achieve high performance . And the control of a strong network of direct sales network managers to better use these networks to reduce the difficulty of team members to develop new markets, thus reducing unit of time, ahead of the completion of business plans. Among the top ten success of direct marketing manager, more than half of the people's own emphasis on team training exception, and bending here.

Third, have a good brand operational capability and crisis management capacity is also very important. Currently, competition in any product will quickly into white-hot stage, whether it is traditional business or to direct the core of direct marketing companies for marketing, are not open around the building a strong corporate branding. The intense competition and improve the system of social control, but also will cause a crisis event there are more difficult to predict, these are all direct sales manager's brand planning capacity and emotional tone ( ability to make a high demand section. 2006 Top Ten success of the perfect leader in direct marketing manager (Chinese) President Hu Rui Lian is to take steps to promote the perfect (China) to promote the work of advanced product development company, completed a strategic goal, which was defined by success of. The Amway (China) General Manager of De-Yin Zheng in the help too processed, "the British Te Laide" incident, and began cleaning up after the doors and severe purging to obtain a greater development platform.

In addition, and business growth closely tied, was the direct manager's "ability to learn." In 1983, the British Shell conducted a survey of Fortune 500 companies how long the life cycle, and the results kept confidential for 15 years announced. The survey shows that these very sophisticated companies on average life expectancy is only 30 to 40 years, less than half of ordinary life; only 20 companies survived for 200 years and is still alive. The survey found that these 20 companies have a common feature of longevity is the strong learning ability. Those who do not know how short-lived study of companies in the world around environmental, technological, and social changes have taken place after, still according to old to do it. Although they financial, technical, personnel and other resources in everything, looks beautiful full, but in fact vulnerable. This shows the vitality of a business from corporate learning ability, and the corporate learning ability, the ability to learn from business people. As a guide the corporate culture, professional managers of learning ability is especially critical. The development of direct selling companies, direct sales manager for corporate look forward to building a high learning ability as the core of corporate culture, thus, direct their own learning ability managers will directly determine the significance of its direct selling business.

One thousand to ten thousand, said, with the direct marketing industry, direct selling business is business first, then we can talk about the characteristics of their business model. This requires managers to know how to direct across direct marketing, commercial understanding, corporate strategy, corporate culture, enterprise system, direct sales team building, corporate brand building, all familiar with. In addition to these solid foundation, rich management experience, good attitude to achieve the direct management of enterprise management to control and, more needs to be an extraordinary learning ability across direct marketing, to break the cocoon into a butterfly, flying over the sea.

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Thursday, September 16, 2010

jsp, servlet talk about Chinese issues

In the jsp, the Chinese people to be terribly upset often garbled.

Common measures for Chinese processing, can often be seen in the main line is the following 2:


Virtual Small Dragon Pavilion is also mainly the above two kinds of methods were modified to become a 1.1 version.

A simple summary of the sample occurred in the Chinese and the following places:

1 with the Chinese in the url parameter can be directly read.

For example:

2 sql database relevant to the operation

Here the use of Access without problems.

3 to read HTML form submitted in the form of Chinese values

Need to be encoded in jswdk the more concise wording such as:

String name1 = new String (request.getParameter ("user_id"). GetBytes ("ISO8859_1"));

In addition, jdk1.3 support, do not join

In jdk1.2.2 below, even if the two kinds of methods used at the same time is also very unstable.

In the resin platform, the situation is better. As long as the first line of the page by adding:

Can correctly handle the Chinese.

If we add the code then it does not.

5 session included the Chinese

In jswdk, the strange thing is, if read from the form of encoded values can be displayed correctly;

However, given directly to Chinese values are not.

resin platform well, ibid.

6 for values of the variables assigned after the Chinese displayed correctly in Chinese.

For example, the following procedures:

Also jswdk1.0.1, above representation is not the problem in jdk1.2.2, but it can not be displayed under jdk1.3.

resin platform well, ibid, tested only in make up

Without the need to also be able to display Chinese correctly.


jswdk may only be used for general development, stability and other issues may not be as commercial software.

As the jdk1.3 version many times better than those jdk1.2.2, and also better support for Chinese, so it should be used.

As a free commercial software, resin is not only fast, stable, and automatically compile, mistakes can be pointed out that the line can support the use of server-side javascript, etc., but at least I think that the support of the Chinese language well.

Of course, if you can not do anything with the right will show the Chinese what we expected.

Also, I believe in the unix / linux / solaris should under no such problem.

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Monday, August 2, 2010

Me introduce the judges to do creative practice contest Hugo

Ali software together CSDN, InfoQ, Javaeye and other well-known technology site, Beida Jade Bird and a number of training institutions, on July 2 was officially launched in Nanjing, "Wang ska - me introduce innovative practice contest" to find the most innovative Internet applications, providing developers the opportunity to achieve a dream for me introduce an open platform for users of fresh fashion to provide the most interactive applications.

"Wang Scar" Creative Practice Competition Competition and product innovation time points two seasons. No. 1 player has begun the season hot application, online selection in August 1 - 8 carried out on 25, participants can design a small plug-in Want Want, interactive games, tools, expression, or skin, so long as the Internet Top applications or services to the Want Want to enable users to need it, used cool.

Gold to create ska Oscar Wong

"Wang Scar" Creative Practice Competition Competition and product innovation time points two seasons. No. 1 player has begun the season hot application, online selection in August 1 - 8 carried out on 25, participate in exclusive prize Jieyou me introduce the most fortunate of five players, not only will be bringing home a symbol of high honor, worth tens of thousands of The "Wang ska" Special Award - Want Want Jin (50g thousands of gold), will in practice be 200,000 start-up stage funding and business sites free of charge.

Network creative originator - Hugo to comment

Learned that the contest organizers invited a number of prosperous ska in software development, network ideas have extensive experience in areas such as appraisal, in which the network Red Hugo as a guest judge, he once said that "" a Steamed The massacre, "" creative popular in the entire Internet. Only the early stages of the race, Wong ska has detonated more than prestigious national college students creative passion, enthusiasm competition has generated a lot of lovely ideas, one after another at me introduce the official online contest on display .

Many independent software developers and internet enthusiasts in the early growth stages, because the lack of startup funds, space and hardware, so many good ideas remain only on paper side of Appeal put into practice; or because of the lack of a sufficient number of success stories can not be quickly and effectively into the software services into end user. Ali software, "Wang ska - me introduce innovative practice of Competition", on the one hand for the developers to provide more creative space and business opportunities, on the other hand, by me introduce an open platform to enable developers to be in excellent products the value of practice, the client, but also to meet all kinds of Internet users growing demand for online applications, enriching the user experience.

Wang ska me introduce innovative practice will be the contest as an opportunity to enhance interaction, expanding openness, innovation, designed to provide users with a wider range of network integration services. Wang ska Creative Practice Competition Registration:

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Monday, July 26, 2010

C + + programmers to easily commit the error of 10 C #

We know, C # and C + + syntax is very similar, from a C + + to C # transformation, the difficulty is not the language itself, but rather familiar. NET-managed environment and on. NET framework for understanding.

Although C # and C + + in grammatical change is very small, almost not have any impact, but some changes are enough to make some careless moment of C + + programmers in mind. In this article we will discuss the C + + programmers the ten most likely to commit errors.

Trap 1: there is no clear end of the method

Almost completely sure that, for most in terms of C + + programmers, C # and C + + the biggest difference is that debris collection. This also means that programmers no longer need to worry about memory leaks and make sure to remove all the useless pointer. But we can no longer accurately control the process kill useless objects. In fact, in C #, there is no clear destructor.

If the use of non-management resources, without the use of these resources, you must explicitly release it. Recessive control of resources by Finalize method (also known as the finalizer) provided, when the object is destroyed, it will be called to recover debris collection program resources occupied by the object.

finalizer should only release the destruction of the object occupied Non-management resources, and other objects should not be involved. If the program is only used to manage resources, it need not be the implementation of Finalize method, only the non-manageability of resources will be used in the treatment of Finalize method. As the need to take up certain resources finalizer, it should only need it to perform the method finalizer.

Directly call an object's Finalize method is not permitted (except in sub-class called base class Finalize Finalize.), Debris collection program will automatically call Finalize.

From the syntax point of view, C # in the destructor and C + + is very similar, but in fact they are completely different. C # the destructor definition of Finalize method is a shortcut. Therefore, the following Erduan code is different:

~ MyClass ()
/ / Need to complete the task

MyClass.Finalize ()
/ / Need to complete the task
base.Finalize ();

Error 2: Finalize and Dispose to use whom?

From the above discussion, we have been very clear, explicit to call the finalizer is not allowed, it can only be called debris collection program. If you want to free up some no longer in use as soon as possible a limited number of non-managed resources (such as file handles), you should use the IDisposable interface, the interface has a Dispose method, which can help you accomplish this task. Dispose is no need to wait for Finalize to be called and be able to release the non-manageability of resources.

If you have used the Dispose method, you should stop the debris collection process and then the corresponding object method implementation of Finalize. To do this, you need to call the static method GC.SuppressFinalize, and the corresponding object pointer passed to it as a parameter, Finalize method can call the Dispose methods. Accordingly, we can get the following code:

public void Dispose ()
/ / Complete clean-up operation

/ / Notify the GC not to call Finalize method
GC.SuppressFinalize (this);

public override void Finalize ()
Dispose ();
base.Finalize ();

For some objects, may call the Close method is more suitable (for example, the document object calls Close on more appropriate than Dispose), you can create a private property of the Dispose method and the Close method of public property, and to call Dispose to realize Close call the Close method of some object.

Given the uncertainty will call Dispose, but the implementation is uncertain finalizer (we can not control when the GC will run), C # provides a Using statement to ensure the Dispose method will be called the earliest possible time. General approach is to define which objects to use, then use brackets for these objects to specify a range of activities, in the event when the innermost parentheses, Dispose method will be automatically invoked, the object for processing.

using System.Drawing;
class Tester
public static void Main ()
using (Font theFont = new Font ("Arial", 10.0f))
/ / Use theFont object

) / / Compiler will call Dispose object processing theFont

Font anotherFont = new Font ("Courier", 12.0f);

using (anotherFont)
/ / Use anotherFont object

) / / Compiler will call Dispose object processing anotherFont



In this case, the first part, Font object is created in the Using statement. When the Using statement at the end, the system will call Dispose, on the Font object for processing. In this case, the second part, Font object is created in the Using statement outside, in the decision to use it, then place it inside the Using statement, when the Using statement at the end, the system will call Dispose.

Using statement can also prevent other accidents from occurring, ensure that the system will call Dispose.

Error 3: C # in the value-type variables and reference-type variables are different

As with C + +, C # is a strongly typed programming language. C #, data types are divided into two categories: C # language itself, the inherent data types and user-defined data types, which is also similar with C + +.

In addition, C # language Hai Ba variables are divided into value types and reference types. Unless it is to be included in a reference type, value type variables retained in the stack, this point and C + +, variables are very similar. Reference type variable is a stack, its value is the address of the object heap, and C + +, the pointer is very similar. Value type variable value is directly passed to the method of reference-type variables are passed as parameters to the method, passing the index.

Classes and interfaces can create reference type variable, but need to point out that structure data type is a built-in C # data types, it is also a value-based data types.

Error 4: Note that implicit data type conversion

Boxing and unboxing enable value data type is used as the index data type using the two processes. Value-type variables can be packaged into an object, and then the return value is unpacked variables. Including built-in data types, including C #, the data of all types can be implicitly converted to an object. Packing a value type variable will generate an object instance, and then copied to the instance variable.

Boxing is implicit, if necessary where the index data type data type using a value type variable, the value of hidden variable will be transformed into the index data type of variable. Boxing will affect the performance of code execution, so should be avoided, especially when the data volume.

If you want to convert a packed object back to the original value type variable, it must be explicit to be unpacked. Unpacking need two steps: First, the object instance checks to ensure they are shaped by the values of variables are packaged into the; second step in the value of the instance to copy the value type variable. In order to ensure a successful solution package was unpacked the object must be packing a value type variable by the value of the index generated objects.

using System;
public class UnboxingTest
public static void Main ()
int i = 123;

/ / Package
object o = i;

/ / Solution Package (must be the dominant)
int j = (int) o;
Console.WriteLine ("j: (0)", j);

If the object is unpacked is not valid, or a different data type object index will result InvalidCastException different things.

Error 5: Structure and objects are different

C + + structures and classes in the almost, the only difference is that by default, the structure of access is public, its inheritance rights is public. Some C + + programmers to structure as a data object, but this is not a convention must be the case.

In C #, the structure is only a user-defined data types, and can not be substituted. Although the structure of the support properties, methods, fields and operators, but does not support inheritance and destructor.

More importantly, the class is an indexed data type, the structure is a value type data type. Therefore, the structure of the index operation in the expression of the target area without more useful. Array of operational structure more efficient, and in the operational aspects of the collection is less efficient. Set to index, structure must be packaged is suitable for use in the operation of the collection, a collection of classes in the large-scale operations more efficient.

Error 6: Virtual methods must be explicitly covered

In the C # language, the programmer of a virtual method in the coverage must be the dominant use of the override key word. Suppose a Window class is written by the A company, ListBox and RadioButton classes by B's and programmers in the company prepared to buy the A Window on the basis of class, prepared, B Company of the programmers of the Window class, including changes in the future little is known about the situation, including the design.

If the B's, a programmer to add a ListBox Sort method:

public class ListBox: Window
public virtual void Sort () (")

A company release a new version in the Window class before, this will not have any problems. A company if the Window class programmers also added a Sort method.

public class Window
/ / "
public virtual void Sort () (")

In C + +,, Windows class will be the ListBox Sort method Sort method of the class based approach, in the hope of calling Windows class Sort method, ListBox class Sort method will be invoked. In C #, virtual function is always considered to be the root of virtual dispatch. In other words, once C # finds a virtual method, you will not find in the virtual chain other virtual methods. If the ListBox is compiled again, the compiler will generate a warning message:

"Class1.cs (54,24): warning CS0114:''ListBox.Sort ()''hides
inherited member''Window.Sort ()''.

For the current members of the original method of coverage, you need to add the override key word, or add new key word.

To remove the warning message, the programmer must find out what he wants. ListBox class can be added before the Sort method new, that it should not override the virtual method in Window:

public class ListBox: Window
public new virtual void Sort () (")

This could clear the warning. If the programmer really want to overwrite methods in the Window, you must use the override key word to demonstrate its intentions explicit.

Error 7: class member variable initialization

C #, C + + initialization and different. Suppose there is a character with a private member variable age of the Person class, Employee class is generated by a succession of Person, and it has a private member variable nature of salaryLevel. In C + +, we can initialize the Employee's constructor initializes some salaryLevel, as shown in the following code:

Employee:: Employee (int theAge, int theSalaryLevel):
Person (theAge) / / initialize base class
salaryLevel (theSalaryLevel) / / initialize member variable
/ / Constructor code

This method in C #, is illegal. While still can initialize base class, but as the code above as initializes the member variable will cause a compiler error. In C #, we can define a member variable to initialize it when the same:

Class Employee: public Person
/ / Member variable definition
private salaryLevel = 3; / / initialization

Note: You must explicitly define each variable access.

Error 8: Boolean variables and integer variables are different from children

if (someFuncWhichReturnsAValue ())

In C #, Boolean variables and integer variables are not the same, so the following code is incorrect:

if (someFuncWhichReturnsAValue ())

if someFuncWhichReturnsAValue return to zero, said false, or that the idea is no longer true. The advantage is that the original assignment operator there will be confused with the same error will not happen again. So the following code:

if (x = 5)

At compile time error occurs because the x = 5 is the 5 assigned to the X, rather than a Boolean value.

Error 9: switch statements would be less than the implementation of some statement

In C #, if a switch statement to implement a number of operations, the program may not perform to the next statement. Thus, while the following code in C + + is legal, but in C #, not legal:

switch (i)
case 4:
CallFuncOne ();
case 5: / / error, will not be executed here
CallSomeFunc ();

To achieve the above purpose of the code needed to use a goto statement:

switch (i)
case 4:
CallFuncOne ();
goto case 5;
case 5:
CallSomeFunc ();

If the case statement does not execute any code, all the statements will be executed. Such as the following code:

switch (i)
case 4: / / can perform to
case 5: / / can perform to
case 6:
CallSomeFunc ();

Error 10: C # in the clear assignment of variables required

In C #, all the variables must be assigned before use. Therefore, you can define variables not initialize it, if it is passed to a method before, must be assigned.

If the only way through the index to pass a variable, and the variable is the method of output variables, this is it will cause problems. For example, suppose there is a method that returns the current time, hour, minute, second, if the write code like this:

int theHour;
int theMinute;
int theSecond;
timeObject.GetTime (ref theHour, ref theMinute, ref theSecond)

If you use theHour, theMinute and theSecond not before the three variables are initialized, it will generate a compiler error:

Use of unassigned local variable''theHour''
Use of unassigned local variable''theMinute''
Use of unassigned local variable''theSecond''

We can initialize these variables to 0 or other methods did not affect the value of the return value to solve this small problem the compiler:

int theHour = 0;
int theMinute = 0;
int theSecond = 0;
timeObject.GetTime (ref theHour, ref theMinute, ref theSecond)

This little too cumbersome, these variables are passed to the GetTime method, then change it. To solve this problem, C # specifically for this situation out parameter modifier provided, it can make an argument without initialization can be cited. For example, GetTime parameters in its own makes no sense, they are just to express the output of the method. Before the method returns, Out parameters must be assigned a value. Here is the revised GetTime methods:

public void GetTime (out int h, out int m, out int s)
h = Hour;
m = Minute;
s = Second;

Here is a new method called GetTime method:

timeObject.GetTime (out theHour, out theMinute, out theSecond);

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Thursday, July 22, 2010

Basic connection fiber optic transceivers

Optical transceiver is a short distance to long distance twisted pair electrical signals and optical signals to be interchanged, Ethernet media conversion modules, in many places, also known as electron converter. Products are generally used in the Ethernet cable can not be covered, you must use optical fiber to extend the transmission distance of the actual network environment, and often located in the broadband MAN access layer applications.

In a traditional Ethernet connection from the role of the media are mainly twisted pair. Twisted pair transmission distance limit of about 200 meters, so a short distance constraints of network development, while twisted-pair influenced by electromagnetic interference, which no doubt the quality of data communication by the greater impact. The use of fiber optic transceivers, Ethernet connection in the media for the fiber. Low-loss optical fiber, high resistance to electromagnetic interference, in the network transmission distance from 200 meters Kuo Zhandao 2 kilometers or even tens of kilometers, hundreds of kilometers of Tong Shi Nai Zhi Yu, Ye Shu Ju communications to Zhiliangyouliao Jiaotaitigao. He makes servers, repeaters, hubs, terminals and terminals connected between the more simple.

In practical applications, fiber optic transceivers are mainly the following three basic connections:

1, ring backbone

Ring backbone network is built using SPANNING TREE characteristics within the metropolitan area backbone, this structure can be deformed as the network structure, suitable for high density metropolitan center of cell to form the core of fault-tolerant backbone network. Ring backbone network characteristics on IEEE.1Q and ISL support, can ensure compatible with most mainstream backbone networks, such as inter-switch VLAN, TRUNK capabilities. Ring backbone network for the financial, government, education and other industries form of broadband virtual private network.

Second, chain backbone

Chain-shaped backbone connection using chain-shaped light can save a lot of key number, for the edge of the city and their suburban areas high-bandwidth low-cost structure of the backbone network, the model also can be used for highways, oil, transmission line other environment. Chain-shaped backbone network characteristics on IEEE802.1Q and ISL support, can ensure compatible with the vast majority of the backbone network for the financial, government, education and other industries form of broadband virtual private network. Chain-shaped backbone network can provide images, voice, data and multimedia real-time monitoring integrated transmission network.

Third, the user access system

Users access the system using adaptive and 10Mbps/100Mbps 10Mbps/100Mbps automatic conversion feature, you can connect any client device, without the need to prepare a variety of fiber-optic transceiver for the network to provide a smooth upgrade. Also use half-duplex / full duplex and half duplex adaptive / full duplex automatic conversion, you can configure the client inexpensive half-duplex HUB, several times lower client network costs, improve the competitiveness of the network operators . Meanwhile, the device built-in switch core to improve the transmission efficiency of access equipment to reduce the network broadcast, control traffic, detect transmission failure.

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