There are two way to check.first is you can directly check whether key contain A or not in binding like this:-. but i think this is not the better way so instead of this you can use ko.computed to check.
Check for operating system information in Windows 7. 1  Click the Start button , enter Computer in the search box, right-click Computer, and then click Properties. 2  Look under Windows edition for the version and edition of Windows that your PC is running.
1 After you click the link, click Download to download the iTunes installer. When prompted, click Save (instead of Run). iTunes 12.1.3 is the latest version of iTunes supported for Windows XP and Vista.  Right click on iTunesSetup or iTunes6464Setup (the installer you downloaded in step 3).