How to take screen shots in windows system using inter systems cache?
Cache doesn't have any built-in way to directly take a screen shot, so the closest you could come is to have a Caché process call something that does know how to take a screen shot. The ways to call out from cache are documented on the Intersystems web site and this same documentation is usually included in a Caché install.
The simplest option (and you don't give enough information to know whether that will work) is probably to call something like $zf(-1,"import -window root screen.jpeg"). In this example, "import -window root screen.jpeg" is a command-line call. $zf(-1) spawns a child process and runs whatever text you give in the second parameter as a command-line call.
I got the specific text for this call from a question on superuser, which you might want to look at if you don't have a screen shot program available that can be called from the command prompt.
If that doesn't work for you, there are other options than $zf(-1) available, but you will probably need to read the linked documentation to decide what works best.