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.
Includes inside the back cover: Inside the back cover of this book you'll find a software download. certificate. The download includes an easy-to-use estimating program. with all the cost estimates in this book. The software will run on PCs. using Windows XP, Vista, 7 or 8 operating systems.