Technology Questions

Wrapping is also called as packing or boxing.

Storing the data inside the object as private data which can accessed outside the class only by using methods.

The .Net runtime knows about all the references between the objects. It can identify all the circular references that are reachable from the root and hence finalize them to free them all at once if and when needed.

There are mainly four type of JDBC drivers available. They are:

Type 1 : JDBC-ODBC Bridge Driver - A JDBC-ODBC bridge provides JDBC API access via one or more ODBC drivers. Note that some ODBC native code and in many cases native database client code must be loaded on each client machine that uses this type of driver. Hence, this kind of driver is generally most appropriate when automatic installation and downloading of a Java technology application is not important. For information on the JDBC-ODBC bridge driver provided by Sun.

Type 2: Native API Partly Java Driver- A native-API partly Java technology-enabled driver converts JDBC calls into calls on the client API for Oracle, Sybase, Informix, DB2, or other DBMS. Note that, like the bridge driver, this style of driver requires that some binary code be loaded on each client machine.

Type 3: Network protocol Driver- A net-protocol fully Java technology-enabled driver translates JDBC API calls into a DBMS-independent net protocol which is then translated to a DBMS protocol by a server. This net server middleware is able to connect all of its Java technology-based clients to many different databases. The specific protocol used depends on the vendor. In general, this is the most flexible JDBC API alternative. It is likely that all vendors of this solution will provide products suitable for Intranet use. In order for these products to also support Internet access they must handle the additional requirements for security, access through firewalls, etc., that the Web imposes. Several vendors are adding JDBC technology-based drivers to their existing database middleware products.

Type 4: JDBC Net pure Java Driver - A native-protocol fully Java technology-enabled driver converts JDBC technology calls into the network protocol used by DBMSs directly. This allows a direct call from the client machine to the DBMS server and is a practical solution for Intranet access. Since many of these protocols are proprietary the database vendors themselves will be the primary source for this style of driver. Several database vendors have these in progress.

Cursor_Already_Open,  Invalid_Cursor.

TTL is a value in data packet of Internet Protocol. It communicates to the network router whether or not the packet should be in the network for too long or discarded. Usually, data packets might not be transmitted to their intended destination within a stipulated period of time. The TTL value is set by a system default value which is an 8-bit binary digit field in the header of the packet. The purpose of TTL is, it would specify certain time limit in seconds, for transmitting the packet header. When the time is exhausted, the packet would be discarded. Each router receives the subtracts count, when the packet is discarded, and when it becomes zero, the router detects the discarded packets and sends a message, Internet Control Message Protocol message back to the originating host.

Use case diagram, activity diagram, Collaboration diagram. 

Use case diagram :

It describes the business environment. Its primary goal is to show the series of events and actions within any given process that will be performed by an actor.  

Activity diagram:

The activity diagram is important because it gives an outline of the work flow within the business as well as the activities and action completed. 

For instance with a company, there is likely to be more than one department. In such a case each department, will have different access levels to the system. 

So if there’s a Medical, HR and Accounts team they will only have access to screens that relate to each. 

The activity diagram will highlight the differences within the departments which will be very helpful for developers when they are designing and coding. 

Collaboration diagram:

A collaboration diagram, also called a communication diagram or interaction diagram, is an illustration of the relationships and interactions among software objects in the Unified Modeling Language (UML). The concept is more than a decade old although it has been refined as modeling paradigms have evolved. 

we can override tostring() method to return String representation of our object data

The following are the usages of the Command object in AD0.NET:

The Command object in AD0.NET executes a command against the database and retrieves a DataReader or DataSet object.

  =>  It also executes the INSERT, UPDATE, or DELETE command against the database.
  =>  All the command objects are derived from the DbCommand class.
  =>  The command object is represented by two classes: SqlCommand and OleDbCommand.
  =>  The Command object provides three methods to execute commands on the database:
  =>  The ExecuteNonQuery() method executes the commands and does not return any value.
  =>  The ExecuteScalar() method returns a single value from a database query.
  =>  The ExecuteReader() method returns a result set by using the DataReader object.