Unit 3 - Multimedia

7. What are the two commonly used Request methods?

The request methods tell the script how it was invoked. Based on this information, the

Script decides how to act. The request method is passed to the script using environment

Variable called REQUEST- METHOD. The two most common request methods used are GET and POST.

GET

GET is a request for data, the same method used for obtaining static documents. The

GET method sends request information as parameter tacked onto the end of the URL. These parameters are passed to the CGI program in the environment variable QUERY-STRING. E.g.: If the script is called myprog.exe and is invoked from a link with the form

<A HREF="cgi-bin/myprog.exe? lname=blow&fname=joe"> The REQUEST_METHOD will be the string GET, and the QUERY_STRING will contain lname=blow & fname=joe. A mandatory question mark separates the name of the script from the beginning of the QUERY_STRING. If a slash is used instead of the question mark; the server passes the information to script using the PATH_INFO variable instead of the QUERY_STRING variable.

POST

POST operation occurs when the browser sends data from a fill-in form to the server.

With POST, the QUERY_STRING mayor may not be blank, depending on the server.The data from a POSTed query gets passed from the server to the script using STDIN. Because STDIN is a stream and the script needs to know how much valid data is waiting, the server also Supplies another variable, CONTENT_LENGTH, to indicate the size in bytes of the incoming "data.

The format for POSTed data is

Variable1=value1 & variable2=value2 &etc.

After the required data is available, the script executes and writes its output to the STDOUT. The MIME code that the server sends to the browser indicates the type of the file that is being sent. This information that precedes the file is usually called the header. Since the script generates the output on the fly the server will not be able to create a header for that information. Hence this information has to be supplied by the script itself. Failure will result in the browser receiving information that it does not know how to display.

8. What do you mean by JDBC?

JDBC Part of the Java Development Kit which defines an application-programming interface for Java for standard SQL access to databases from Java programs.

9. Define ODBC.

It is a standard for accessing different database systems. There are interfaces for Visual Basic, Visual C++, SQL and the ODBC driver pack contains drivers for the Access, Paradox, dBase, Text, Excel and Betrieve databases.

10. List any two keyboard events?

1. OnKeypress

2 .onKeyUp

3. OnKeyDown

11. List any two mouse events?

l. onMouseUp

2. OnMouseDown

3. OnMouseOver

4. OnClick