Explain Console Application .
Console applications are command line oriented applications that allow user to read characters from the· console, write characters to the console.
Console applications are typically designed without graphical user interface and are compiled in a stand-alone executable file.
A console application is run from the command line with input and output information being exchanged between the command prompt and the running application. Because information can be written to and read from .the console window, this makes the console application a great way to learn new programming techniques without having to be concerned with the user interface.
A web service is an extension of ActiveX. Those programmers, who have used ASP and JSP both, know the apparent shortcomings of ASP. JSP has been enriched with the concepts of Beans. And Tags. ASP equivalent for Beans and Tags was ActiveX Controls. and ActiveX automation servers. Let me take a minute to explain this point a bit further. Web Services is NOT a Microsoft proprietary standard. It is a W3Consortium standard, and has been developed by Microsoft, IBM and many other big names of the industry.
Functions are of two types. The ASP built-in functions and the programmer defined implemented functions. In order to use the built in functions you just need to pass the appropriate parameters and make a simple call to these functions. The functions are implemented by the ASP itself. The string manipulation functions, Number conversion functions are an, example of built in functions.
The user-defined functions are the functions that are defined and implemented by the programmer. A programmer can either write these functions in the same asp file or can write them in another file. If the function code resides in the same asp file then the programmer can directly call that function. In case the function resides in another file, say "func.asp"; then the programmer needs to include that file by writing a statement like ; and now the programmer can use the function. The programmers can also make ActiveX automation servers, and call various functions of these ActiveX servers, But one limitation is very obvious - no matter which type of function you use, the function MUST physically reside on the same machine. For example your ActiveX automation server must be implemented either as a .dll or as an .exe and then must also be registered in Windows Registry before an asp code can call its functions.
In a world where the Intemet has become not only a necessity but also a way of life – it is obvious that this limitation is a strong one; Microsoft's answer to this problem is "Web Services". The idea goes something like this:
1. The Web service provider develops a useful function(s), and publish/advertise it. The
Web Service provider uses Web Service Description Language (WSDL) standard to describe the interface of the function(s). This is much like the Type Libraries (TLB) and Object Description Language files (ODL) that needs to be generated with the ActiveX automation servers.
2. The programmer/client who needs the function does a lookup by using a process called
- Web Service Discovery or SOAP Discovery (also called DISCO for Web Service DISCOvery)
3. The Actual communication between the client program and the web service takes place through a protocol called Simple Object Access Protocol (SOAP) -SOAP is an XML based light weight protocol used for communication in a decentralized distributed environment.