Location of the operating system in memory

Galvin says:

We can place the operating system in both low memory and high memory. The main factor influencing this decision is the location of the interrupt vector. Since the interrupt vector is usually located in low memory, programmers usually also place the operating system in low memory.

I'm not quite sure how the location of the interrupt vector affects the location of the OS in memory. I tried to go to Google, but could not find anything to my satisfaction. Can someone clarify this.