draggable and zoomable maps

[Josef Feit]

Hi,

I would like to know how the systems for the maps are working.

I wonder how the updating of the tiles of the map is achieved. I can
imagine the DIV being drawn, the visibility of individual tiles being
checked and - if some new are visible, the src of their image being
updated etc.

But how the grid of tiles is created? Are the new rows and columns of
tiles added dynamically when they are dragged into visible area? Or they
are created in advance?

Can somebody point me to some resources, tutorials or examples? There is
a plenty of info on the web, but usually in the form of ready to use
libraries, often too complicated; they explain how to use the libraries
and not how the functions work.

I would rather need to understand how it works and eventually use it to
access the details of large images of my own - I do not need to attach
to geographical servers.

Thanks
Josef