If you want to check if your PC has the most recent update of Windows
Operating System : (Windows 10)
3. Click "Update and Security"
4. From Windows Update > Click "Check for Updates" button
If your PC’s Windows Operating System is updated it will notify you like the sample below
NOTE: The message may say "you are up to date. However, unless the date is "today" there could be pending updates. This simply means your computer is up to date for the time that it was checked. Go ahead and click on the "Check for updates" button to see if there are pending updates. If so, install them.
Windows Update FAQ link below also applies for other Windows Version like Windows 7 and Windows 8.1
Link for Reference : https://support.microsoft.com/en-au/help/12373/windows-update-faq