14.11.2012 Views

PC Architecture. A book by Michael B. Karbo

PC Architecture. A book by Michael B. Karbo

PC Architecture. A book by Michael B. Karbo

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Copyright <strong>Michael</strong> <strong>Karbo</strong> and ELI Aps., Denmark, Europe.<br />

● Next chapter.<br />

● Previous chapter.<br />

Chapter 12. Data and instructions<br />

Now it’s time to look more closely at the work of the CPU. After all, what does it actually do?<br />

Instructions and data<br />

Our CPU processes instructions and data. It receives orders from the software. The CPU is fed a gentle<br />

stream of binary data via the RAM.<br />

These instructions can also be called program code. They include the commands which you constantly<br />

– via user programs – send to your <strong>PC</strong> using your keyboard and mouse. Commands to print, save,<br />

open, etc.<br />

Data is typically user data. Think about that email you are writing. The actual contents (the text, the<br />

letters) is user data. But when you and your software say “send”, your are sending program code<br />

(instructions) to the processor:<br />

Fig. 80. The instructions process the user data.<br />

Instructions and compatibility<br />

Instructions are binary code which the CPU can understand. Binary code (machine code) is the<br />

mechanism <strong>by</strong> which <strong>PC</strong> programs communicate with the processor.<br />

All processors, whether they are in <strong>PC</strong>’s or other types of computers, work with a particular instruction<br />

set. These instructions are the language that the CPU understands, and thus all programs have to<br />

communicate using these instructions. Here is a simplified example of some “machine code” –<br />

instructions written in the language the processor understands:<br />

proc near

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!