Specifications

Your computer is designed to communicate with peripherals by
way of the connectors on the rear panel of the main system
unit. The connectors are called “ports,” and allow information
to be sent back and forth between the system CPU and a
peripheral device.
Your keyboard and video monitor connect to the main system
unit by way of two specialized ports. The keyboard is connected
to the “Keyboard port” on the rear panel of the main system
unit. If you have purchased a video monitor system for your
computer, the display monitor is connected to the “video port”
on the rear panel of the video controller card, which is
mounted inside your main system unit.
Since your system CPU must be in constant communication
with both the keyboard and the display monitor, specific
circuits connect them together. Since other peripheral devices
only communicate with the system CPU occasionally, they can
use general purpose ports.
Computerized data is composed of electronic words called
“bytes.” As an example, each letter or number that appears on
your display monitor has been sent from the main system unit
to the monitor itself in the form of a single byte. This byte is
made up of individual “bits.
” in the same way that a word is
made up of individual “bits” in the same way that a word is
system CPU, bytes are made up of groups of eight bits. Using
eight-bit bytes results in 256 basic combinations, each of which
corresponds with a specific letter or number.
7-2 Expanding Y OUY System