Hi Neha,
> [...] if i use TC as com object than i would be able to work on my machine simultaneously with automation ,like Selenium.
Just to clarify: the case is not that TestComplete somehow blocks you from using your workstation when the tests are executed, but the case is that if tests emulate the work of the regular user (i.e. work with the tested application using its UI), then the mouse and keyboard are used to provide the input to the application. If you use mouse and keyboard at the same time, this will break input data flow for the tested application and fail the test.
The situation is absolutely the same as if you and your colleague were sitting before the monitor and try to do something by using the same keyboard and mouse concurrently.
The is no problem to use the workstation if the test does not interact with the UI. (For example, if the test interacts with some COM object or interacts with the web service by sending http requests.)
I am not Selenium expert, but pretty sure that the situation with it is exactly the same as with TestComplete.
