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.
Note: If you do own a copy of the latest version of Microsoft Works, version 9, and need to open a WPS file created with Microsoft Works version 4 or 4.5, you'll need to first install the free Microsoft Works 4 File Converter. However, I don't have a valid download link for that program.