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 Sign in with your Microsoft account. 2  In the sign-in menu, click Downloads, product Keys, and subscriptions. 3  Find your software purchase, then click Download.  If a dialog box pops up, click Run to start the installation.