【正文】 。 the release connects In button code as follows: 19 Dim i As integer Dim j as integer Set parm_jobid = New Set mymand = New \39。 opens connects Joins the code as follows in window UNLOAD: 39。 pwd=\ 39。 Produces one connects strCnn = \ DSN=MYDSN。 result collection Dim strCnn As String 39。 parameter 1 Dim parm_joblvl As 39。 connects Dim mymand As 39。 7. The logarithm according to carries on processing。 18 5. The foundation parameter and establishes each parameter the attribute。 Also may use in VB the data object, like RDO (longdistance data object), 17 DAO (data visit object), ADO (ActiveX data object), this method realizes conveniently, quickly, but flexible worse somewhat. As a result of memory process in realization data merit and so on seal, hideaway as well as code pre translation, reduced work load, maintenance convenience, therefore does by many RDBMS and the programming tool the support. In VB each 類數(shù) also provides to saves the process according to the object the support. We as regularly explain its realization take ADO the step 1. Foundation, debugging memory process. You may also be allowed to hang the procedure in the database outside other under the support carry on the memory process the foundation and the debugging work. In this example memory process code is as follows (uses in PUBS MS SQL the example storehouse): CREATE PROCEDURE myprocedure job_id smallint, job_lvl tinyint AS SELECT * FROM employee WHERE job_id job_id AND job_lvl job_lvl 2. Produces one new project in VB, the project has one window, one COMMAND (NAME: COMMAND1) button, one MSFlexGrid (NAME: MSFlexGrid1) controls. 3. The foundation connects ADO connection。 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。 Data Source= student information = selet * from student result order by result 39。 Establishes ADO controls the connection character string and the initial record source, namely demonstration content = Provider=。 withdraws the character string array which the record pendium uses Private Sub Form_Load () 39。 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 Explicit Dim SelectedSeries as Integer 39。s test result, includes the student number, the name, the result 3 fields, the result field form is the character, the value is is superior , is good , center , the difference center one. Window Form1 includes one MSChart controls MC$score, the type for the twodimensional cake chart, uses in to demonstrate each kind of result the student counts。 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 2020 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 works based on the volume of their traffic. The differences are summarized in . Item Circuit Switched Packet Switched Call setup Required Not needed Dedicated physical path Yes No Each packet follows the same route Yes No Packets arrive in order Yes No Is a switch crash fatal Yes No Bandwidth available Fixed Dynamic 12 Time of possible congestion At setup time On every packet Potentially wasted bandwidth Yes No Storeandforward transmission No Yes Transparency Yes No Charging Per minute Per packet Both 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