Memory

Most people know that a computer has memory. But what does that really mean? You often hear techies toss around numbers like ―60GB hard drive.‖ Okay, that sounds impressive, but what does it tell you? This lesson breaks memory into measurable units.

The first thing you need to know is that, at its most basic level, a computer only understands the concept of ―on and off.‖ On is represented by the number one (1); off is represented by the number zero (0). Everything that a computer does is based on this combination of ones and zeros, which is known as the binary system. These ones and zeros are digits, known as bits, which are the smallest memory unit. The term bit is short for binary digit.

The second thing you need to know is that a computer saves information in bytes, not bits. So what is a byte? The term byte is short for binary digits eight. So one byte is made up of eight bits. And a byte is the equivalent of a character, which can be a letter, a number, or a symbol. So let’s say that you’re a self-involved poet whose latest creation is simply titled ―I.‖ That one-word title would equal one byte.

Of course, it would be fairly tedious if a computer stored everything in single bytes. The next largest unit is the kilobyte. A kilobyte (abbreviated K or KB) equals 1,024 bytes or characters. Now let’s say you’re a short-story writer. The one-page, double-spaced masterpiece you submit to your editor would be the equivalent of a kilobyte.

After the kilobyte, the next largest unit is the megabyte. A megabyte (abbreviated M or MB) equals 1,048,576 bytes or characters. If you were a novelist, your latest bestseller would equal a megabyte.

The next unit after the megabyte is the gigabyte. A gigabyte (abbreviated G or GB) equals 1,073,741,824 bytes or characters. Let’s pretend you are a researcher. A whole shelf of books devoted to your favorite subject would be the equivalent of a gigabyte.

Finally, after the gigabyte comes the terabyte. A terabyte (abbreviated T or TB) equals 1,099,511,627,776 bytes or characters. Let’s imagine that you’re an egomaniac who owns an entire bookstore filled only with books by authors you like. Such a single-minded store would be the equivalent of a terabyte.

Table 2-2: Bits and Bytes