CompTIA A+ Certification All-in-One Exam Guide

Figure 5-6 Everything connecting
It’s not too hard to swallow the concept that the CPU uses the address bus
to talk to the devices, but how does it know what to say to them? How does it
know all of the patterns of ones and zeros to place on the address bus to tell
the hard drive it needs to send a file? Let’s look at the interaction between the
keyboard and CPU for insight into this process.
Talking to the Keyboard
The keyboard provides a great example of how the buses and support
programming help the CPU get the job done. In early computers, the
keyboard connected to the data bus via a special chip known as the keyboard
controller. Don’t bother looking for this chip on your motherboard—the
chipset handles keyboard controller functions. The way the keyboard
controller—or technically, the keyboard controller circuitry—works with the
CPU, however, has changed only a small amount in the past decades, making