Information Technology Reference
In-Depth Information
10.
The CPU tells main memory to send the sum (from location
C) to the monitor for display.
Although this outline of work is tedious to write (and read),
these steps emphasize the division of labor in a simple computer.
Except for the physical operation of input (typing) or output (form
ing characters on the screen or on paper), the CPU controls every
activity. Further, the CPU does the actual data processing (e.g., addi
tion). To support such processing, main memory holds data both
before and after the CPU does the actual work.
Finally, input devices (e.g., a keyboard) gather data, notify the
CPU when data are available, and provide that data for transfer to
main memory. Similarly, output devices (e.g., a monitor) display or
save data, obtained from main memory, as directed by the CPU.
Schematically, this entire processing of entering, adding, and dis
playing numbers is shown in Figure 1.1.
Main Memory
CPU
CPU Register Area
1
8
4
6
First Typed Number
2
Location A
Add
3. Notify
CPU
Second Typed Number
7
Keyboard
5
4
Location B
9
5
10
Display Monitor
Location C
Figure 1.1
Reading, adding, and displaying numbers.
