【正文】 Changes ADO controls the record source and renovates =Rs (SeletedSeries)End Sub VB does for the rapid application development (RAD) the tool more and more obtains the development personnel39。 Establishes ADO controls the connection character string and the initial record source, namely demonstration content = Provider=。 One DataGrid controls DgScore uses in by the form form demonstration database content.The work process is: Double strikes the cake chart some region, then DgScore demonstrates the corresponding result the student name list.Code as follows:Option ExplicitDim SelectedSeries as Integer 39。 in the latter, the carrier does. It is this transparency that allows voice, data, and fax to coexist within the phone system.A final difference between circuit and packet switching is the charging algorithm. With circuit switching, charging has historically been based on distance and time. For mobile phones, distance usually does not play a role, except for international calls, and time plays only a minor role(., a calling plan with 2000 free minutes costs more than one with 1000 free minutes and sometimes night or weekend calls are cheaper than normal).With packet switching, connect time is not an issue, but the volume of traffic sometimes is. For home users, ISPs usually charge a flat monthly rate because it is less work for them and their customers can understand this model easily, but backbone carriers charge regional networks based on the volume of their traffic. The differences are summarized in .ItemCircuit SwitchedPacket SwitchedCall setupRequiredNot neededDedicated physical pathYesNoEach packet follows the same routeYesNoPackets arrive in orderYesNoIs a switch crash fatalYesNoBandwidth availableFixedDynamicTime of possible congestionAt setup timeOn every packetPotentially wasted bandwidthYesNoStoreandforward transmissionNoYesTransparencyYesNoChargingPer minutePer packetBoth circuit switching and packet switching are important enough that we will e back to them shortly and describe the various technologies used in detail. THE MOBILE TELEPHONE SYSTEMThe traditional telephone system(even if it some day gets multigigabit endtoend fiber) will still not be able to satisfy a growing group of users :people on the go .People now expect to make phone calls from airplanes ,cars ,swimming pools ,and while jogging in the park .Within a few years they will also expect to send and surf the Web from all these locations and more consequently ,there is a tremendous amount of interest in wireless telephony .In the following sections we will study this topic in some detail.Wireless telephones e in two basic varieties :cordless phones and mobile phones(sometimes called cell phones),Cordless phones are devices consisting of a base station and a handset sold as a set for use within the home. These are never used for networking ,so we will not examine them further .Instead we will concentrate on the mobile system ,which is used for wide area voice and data munication.Mobile phones have gone through three distinct generations ,with different technologies:Analog voiceDigital voiceDigital voice and data(Internet , ,etc.).Although most of our discussion will be about the technology of these systems ,it is interesting to note how political and tiny marketing decisions can have a huge impact .The first mobile system was devised in the . by ATamp。汪老師給了我很大的幫助，使我得到了很大的提高，這對于我以后的工作和學習有非常大的幫助，非常感謝他的耐心指導。5 總結本文從P，V操作實現進程同步與互斥出發(fā)，研究了操作系統(tǒng)中經典的同步問題生產者消費者問題，提出了解決此問題的模型及解決方案，并設計了基于microsoft visual c++而開發(fā)，在WINDOWS 98/2000/XP上運行的操作系統(tǒng)進程管理演示系統(tǒng)（生產者消費者）。 當循環(huán)緩沖區(qū)滿時,生產者線程阻塞。在單緩沖區(qū)中沒有數據的情況下,如果有消費者到達,這時該消費者阻塞。但要注意,不論是生產者之間,消費者之間,還是生產者與消費者之間,他們對于臨界資源──緩沖區(qū)的訪問必須是互斥的,也就是說,在1個生產者或消費者線程訪問完該緩沖區(qū)之前,是決不允許其它的生產者或消費者線程訪問的。消費者進程的活動為:先判斷該單緩沖區(qū)中是否有數據(即是否滿) ,如果沒有,那么它就自我阻塞。2. 多生產者多消費者問題模型。 如果當前沒有產品可以消費, 則等待生產者放產品并讓出監(jiān)控器, 當生產者放了貨物后喚醒它[14]。生產者放一個產品, 就在生產者當前指針位置的方框用紅色填充, 指針順時針前進一格, 指向下一個可以放產品的緩沖區(qū)。為方便觀察生產和消費進展情況, 設置了兩個時間控制變量控制生產者和消費者的生產和消費周期( 即: 線程的run 方法) , 它們是用兩個文本輸入框分別實現數據輸入的。 (true)。 m_PArray[i]=0。i++) { m_hFullSemaphore[i]=CreateSemaphore(NULL,0,1,NULL)。 } } else MessageBox(消費者數目必須在110之間,出錯了)。 thism_CT[i] =new CConsumerThread(this,str)。 CString str。 thism_continue=true。 VERIFY(thism_PT[i]SetThreadPriority(THREAD_PRIORITY_IDLE))。 ithism_np。amp。 MFC界面效果這是系統(tǒng)界面設計的截圖： MFC界面界面上有2個靜態(tài)文本，2個編輯框和7個按紐組成：1. 啟動生產者按紐的代碼：void CPCDlg::OnPstar() { UpdateData(true)?？蚣芑蛘哂善浔旧硖幚硎录灰蕾嚦绦騿T的代碼；或者調用程序員的代碼來處理應用程序特定的事件。雖然，這些內部處理對程序員來說是透明的，但是，懂得和理解MFC內部機制有助于寫出功能靈活而強大的程序。例如，SDI應用程序的模板，MDI應用程序的模板，規(guī)則DLL應用程序的模板，擴展DLL應用程序的模板，OLE/ACTIVEX應用程序的模板，等等。本書將充分的展示MFC調用虛擬函數和消息處理函數的內幕，讓讀者對MFC的編程接口有清晰的理解。于是，MFC建立了消息映射機制，以一種富有效率、便于使用的手段解決消息處理函數的動態(tài)約束問題。3．虛擬函數和動態(tài)約束 MFC以“C++”為基礎，自然支持虛擬函數和動態(tài)約束。MFC中，任何可以處理消息的類都從CCmdTarget派生。CObject是MFC的根類，絕大多數MFC類是其派生的，包括CCmdTarget。MFC的OLE類封裝了OLE API大量的復雜工作，這些類提供了實現OLE的更高級接口。MFC把許多類似的處理封裝起來，替程序員完成這些工作。這些類或者封裝了Win32應用程序編程接口，或者封裝了應用程序的概念，或者封裝了OLE特性，或者封裝了ODBC和DAO數據訪問的功能，等等，分述如下。因為總體上，MFC框架定義了應用程序的輪廓，并提供了用戶接口的標準實現方法，程序員所要做的就是通過預定義的接口把具體應用程序特有的東西填入這個輪廓。 Sleep(t*100)。 srand( (unsigned)time( NULL ) )。 pDlgm_Array[temp]=0。 srand( (unsigned)time( NULL ) )。while(pDlgm_continue){ DWORD temp=WaitForMultipleObjects(SIZE_OF_BUFFER,pDlgm_hFullSemaphore,FALSE,INFINITE)。 pDlg=(CPCDlg*)thism_Parent。 Sleep(t*100)。 srand( (unsigned)time( NULL ) )。 pDlgm_Array[temp]=1。 srand( (unsigned)time( NULL ) )。 while(pDlgm_continue){ DWORD temp=WaitForMultipleObjects(SIZE_OF_BUFFER,pDlgm_hEmptySemaphore,FALSE,INFINITE)。 生產者模擬函數代碼 int CProducerThread::Run() { CPCDlg *pDlg。3 系統(tǒng)實現 程序結構程序分為一個主函數、分別用于模擬消費和生產者的兩個函數以及三個輔助性的函數。V (MuxCustomer) 釋放對滿緩沖資源獨占使用；V(Empty)產生一個空白緩沖區(qū)進行數據處理。消費者算法:做好接收準備。設兩個互斥量MuxPr