Not everybody has exactly the same hardware. But those of you who have a desktop system, like the example shown in Figure 1, probably have most of the components shown in that same figure. Those of you with notebook computers probably have most of the same components. Only in your case the components are all integrated into a single book-sized portable unit.
The system unit is the actual computer; everything else is called a peripheral device. Your computer's system unit probably has at least one floppy disk drive, and one CD or DVD drive, into which you can insert floppy disks and CDs. There's another disk drive, called the hard disk inside the system unit, as shown in Figure 2. You can't remove that disk, or even see it. But it's there. And everything that's currently "in your computer" is actually stored on that hard disk. (We know this because there is no place else inside the computer where you can store information!).
Random Access Memory (RAM)
So if RAM is so fast, why not put everything in it? Why have a hard disk at all? The answer to that lies in the fact that RAM is volatile. As soon as the computer is shut off, whether intentionally or by an accidental power outage, every thing in RAM disappears, just as quickly as a light bulb goes out when the plug is pulled. So you don't want to rely on RAM to hold everything. A disk, on the other hand, holds its information whether the power is on or off.
The Hard Disk
- Point: To point to an item means to move the mouse pointer so that it's touching the item.
- Click: Point to the item, then tap (press and release) the left mouse button.
- Double-click: Point to the item, and tap the left mouse button twice in rapid succession - click-click as fast as you can.
- Right-click: Point to the item, then tap the mouse button on the right.
- Drag: Point to an item, then hold down the left mouse button as you move the mouse. To drop the item, release the left mouse button.
- Right-drag: Point to an item, then hold down the right mouse button as you move the mouse. To drop the item, release the right mouse button.