These definitions are widely used throughout science and technology – not just with computers. We need to know these terms in order to communicate how computers handle data, or information.
Numbers: These numeric prefixes are widely used. Youll notice them everywhere, so know them well. Knowledge is Power!
| Prefix | Value | Examples |
|---|---|---|
| nano- |
0.000000001
or 1 x 10-9 |
Wavelengths of light and atoms are measured in nanometers (nm), billionths of a meter. |
| micro- |
0.000001
or 1 x 10-6 |
It would take one million microliters of water to fill a one liter water bottle. |
| milli- |
0.001
or 1 x 10-3 |
Vitamins are sold in milligrams (mg), or thousandths of a gram. Take 500 milligrams of vitamin C the next time you get a cold. |
| kilo- |
1,000
or 1 x 103 |
A kilometer is a thousand meters (or about 0.6 miles). A kilobyte (kB) is a thousand bytes. This document takes about 5 kB of memory on disk. |
| mega- |
1,000,000
or 1 x 106 |
A megabyte (MB) is a million bytes. A floppy disk holds 1.44
MB of information. |
| giga- |
1,000,000,000
or 1 x 109 |
Computer hard drives are measured in gigabytes (GB). A gigabyte is a billion bytes. My computer has an 18 GB hard drive. |
Above are the most commonly used prefixes, although there are many more, such as pico- (0.000000000001 0r 1 x 10-12), centi- (0.01 or 1 x 10-2) and tera- (1,000,000,000,000 or 1 x 1012).
Transistor: Transistors are tiny devices that can hold a small electrical charge. In a computer, no charge represents a zero and a transistor with an electrical charge represents a one. Their small size, low power needs and relatively low cost make them ideal for holding information in your computer.
Integrated Circuit: Also known as an IC or a chip, an integrated circuit is many interconnected transistors and other simple electronic components. ICs are constructed ("fabricated") on a small rectangle cut from a Silicon wafer, or chip. In 1986 the first one megabyte RAM chip was introduced, which contained more than one million transistors.
RAM: This is the type of memory that a computer uses to temporarily store information to perform high-speed calculations. It is entirely electronic, with no moving pieces, so it is very fast. RAM is made from millions of transistors put together to form a certain type of integrated circuit called a RAM chip. You can add more RAM chips to your computer if it doesn't have enough memory to perform tasks (such as playing movies) where lots of information must be processed by your computer. RAM stands for Random Access Memory, but this name alone is not a sufficient definition.
Bit: Bit stands for Binary digIT. Each number that a computer "thinks" with, whether a zero or a one, is called a bit. A group of 8 zeros and ones is called 8 bits.
| 0 or 1 |
1 bit |
| 0110 |
4 bits |
| 01101101 |
8 bits |
How can computers be so smart when they only know ones and zeroes?
A computer's transistors only register the presence or absence of a given voltage – the computer does not sense "partially on." All values, whether colors, sounds or numbers, are described by zeros and ones. The more zeros and ones you use to describe something, the more accurate that representation will be.
Machines don't get bored with repetitious tasks. What makes a computer so smart is that it can perform billions and billions of repetitious tasks, using only patterns of zeroes and ones which can convey more detailed information.
Think about it as if a computer is made up of many tiny electrical switches. Each electrical switch can only have two values:
1 = On 0 = Off
1 byte = 8 bits
|
|
1
byte |
Since a computer can only think in zeros and ones, there must be a way for it to describe the decimal numbers that we use. You will not be expected to do these conversions, but this explains how one number system translates into another.
|
|
|
"Base 10" Numbers Expressed in Scientific Notation |
"Base 2" Numbers Expressed in Scientific Notation |
| 0 |
0 |
0 |
0 |
| 1 |
1 |
1x100 |
1x20 |
| 2 |
10 |
1x100 + 1x100 |
1x21 |
| 3 |
11 |
1x100
+ 1x100 + 1x100 |
1x21 + 1x20 |
| 4 |
100 |
4x100 |
1x22 |
| 5 |
101 |
5x100 |
1x22 + 1x20 |
| 6 |
110 |
6x100 |
1x22 + 1x21 |
| 7 |
111 |
7x100 |
1x22 + 1x21 + 1x20 |
| 8 |
1000 |
8x100 |
1x23 |
| 9 |
1001 |
9x100 |
1x23 + 1x20 |
| 10 |
1010 |
1x101 |
1x23 + 1x21 |
Example:
Q: What number is 101111 (binary) in the decimal system?
A: Use the powers of two to add up each digit:
| 1 |
0 |
1 |
1 |
1 |
1 |
| 1x25 = 32 |
0x24 = 0x16 = 0 |
1x23 = 8 |
1x22 = 4 |
1x21 = 2 |
1x20 = 1 |
32 + 0 + 8 + 4 + 2 + 1 = 47
American Standard Code for Information Interchange
This generally refers to ACSII-8, where each character of the code is represented by a byte. 1 byte = 8 bits = 2x2x2x2x2x2x2x2 = 28 = 256 values
Therefore, ASCII-8 is limited to 256 different characters.
| Character |
ASCII Bit Pattern |
| A |
0100 0001 |
| B |
0100 0010 |
| C |
0100 0011 |
| a |
0110 0001 |
| b |
0110 0010 |
| c |
0110 0011 |
| ? |
1011 1100 |
| $ |
0010 0100 |
| 1 |
0011 0001 |
| 2 |
0011 0010 |
| 9 |
0011 1001 |
Digital: Digital information only has specific values such as zero and one, but no fractional values. The digital music contained on a CD is broken into specific tones which sound almost as rich as analog sound when millions of them are combined together. A CD plays 44,100 tones per second, while a record player is continuously varying the tones it plays.
Analog: The analog sound we create when we talk or play a record is not limited to specific tones that we may use. An analog image can contain all the colors of the rainbow, even colors that human eyes can't see, while a digital image has a limited number of specific colors, determined by how much memory the computer uses to store or display the image. Analog information and analog signals contain continuous data with infinite shades and fractions in between. Since this type of information is "pure and unfiltered," it also has the disadvantage of being susceptible to unwanted noise, static or blemishes.
© Copyright 1999-2004, Kevin Pedersen. All rights reserved.