This chip is called the central processing unit because this is where most of the processing takes place. The microprocessor depends on other components to perform many specialised functions.

For instance, it needs random-access memory (RAM) as a temporary storage space to hold the programs and files with which it is working currently.

The microprocessor also needs a hard drive or diskettes for permanent data storage, a keyboard for data entry and a monitor to display the data.

Other extras, such as modems and sound cards, let the computer exchange information over telephone lines or play music.

1. When you depress the letter H your keyboard uses its own microprocessor to pick up the signal and translate it into language the system understands. The signal is transmitted to the PC via a cable that connects to a port at the back of the computer.

2. Inside your computer, the letter travels to the computer's microprocessor, which is a very busy chip. Before it can process the letter "H", it must first finish processing data that was requested earlier. Thus, the "H" first travels to a RAM buffer, which is like a waiting room for information. The "H" should not have to wait too long; keystrokes are assigned one of the highest processing priorities in your computer.

3. When the "H" reaches the microprocessor, the microprocessor translates they keystroke into information your monitor can understand. The microprocessor passes the signal on to the video adapter card, a circuit board that controls your monitor. The video card then passes the information along to the monitor, where the image is placed on the screen through a combination of blue, green, and red dots. Each blue, red, and green dot is known as a pixel.

4. What happens when you want to save the information? When you open the file menu and select the save option, the software gets involved. The letters on-screen go to a buffer, and the software, which is temporarily stored in RAM, grabs the data in order to save it. The request then travels to the microprocessor, where the data is processed and passed to the hard drive. Inside the hard drive, a read/write head magnetically stores the information on platters which look like miniature records.

5. All this happens at lightning-fast speed. The more powerful your hardware components, the faster the data appears on-screen and files are saved.