how does operating systems link in with control of software?

Answer 1

The operating system is actually designed to control the flow of information and instructions across the CPU. It determines what system calls have priority when they ask for resources (memory, IO, CPU time). What many users know as "WindowsXP" or the Mac OS is merely a GUI (Graphical User Interface) that adds features to the OS itself. In other words, much of what comes pre-installed with your operating system is NOT part of the operating system itself but merely another program that's added in as part of the "bells and whistles" package.