SIMPOL Documentation

There are a number of differences between the different web server loading methods. Both the CGI and ISAPI approaches use a main() function that takes a cgicall cgi parameter. The main difference between the two is what the current directory is. For CGI programs, the current directory is the same as the location of the program that is being loaded, while for ISAPI programs, they normally start in the %SYS32 directory.

The Fast-CGI program is quite different to the other two, though like with CGI, the location of the program file is also the location of the current directory. Instead of a main(), there are three separate functions. They are: fcgiinit(), which takes no parameters, fcgi(), which takes a cgicall cgi parameter, and an optional type(*) <paramname> parameter, which is the return value from the fcgiinit() function. Finally, there is an fcgiterm() function that takes the return value from the fcgiinit() function to allow any required clean up to take place. One example of this might be if a dynamically loaded library is opened during initialization and in that some memory is reserved. Then during the clean up phase that memory could be released. In most SIMPOL web server programs, there will be little need for the final function, except as an empty function so that it can be called although it will do nothing.

It is also worth mentioning that with advent of what has been called Web 2.0 that by using client-side JavaScript and a capability known as AJAX (Asynchronous JavaScript and XML) a new approach to web server applications has arisen, that are more about handling data requests and sending back the data in a specific form. This technique makes use of the XMLHttpRequest which, in spite of its name, does not need to use XML. It can transfer data in other ways beside using XML. The interesting part of this approach is that of sending pages back every time a call is made to the web server, the application running in the web browser may only send out data requests to refresh what is shown on the page being displayed. This is far more efficient than sending along the entire page each time you send the data. There are two aspects of Web 2.0 really, one is related to this ability to update the data on the page without resending the page, the other has to do with the use of a modern set of libraries to make web applications look more like desktop applications and is embedded into various JavaScript frameworks. JavaScript is still a frustratingly messy language, but it is showing signs of growth. It remains to be seen how long it will take before it becomes easy to create an application the way you want, rather than the way they want.