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

There's too much "stuff" on your computer's hard disk to use it all at the same time. During the average session sitting at the computer, you'll probably use only a small amount of all that's available. The stuff you're working with at any given moment is stored in random access memory (often abbreviated RAM, and often called simply "memory"). The advantage using RAM to store whatever you're working on at the moment is that RAM is very fast. Much faster than any disk. For you, "fast" translates to less time waiting and more time being productive

Abbreviation
Stands for
Spoken as
Approximate #
Actual #
K
Kilo kay or killa
1,000 (a thousand)
1,024
M
Mega
meg
1,000,000 (a million)
1,048,576
G
Giga
gig or giga
1,000,000,000 (a billion)
1,073,741,824

T=Tera=trillion

Example
Size
Or about...
The picture shown in Figure 1
61 KB
61,000 bytes
This entire Web page