Megabytes, Gigabytes, Terabytes… What Are They?
These terms are usually used in the world of computing to describe disk space, or data storage space, and system
memory. For instance, just a few years ago we were describing hard drive space using the term Megabytes. Today,
Gigabytes is the most common term being used to describe the size of a hard drive. In the not so distant future,
Terabyte will be a common term. But what are they? This is where it gets quite confusing because there are at least
three accepted definitions of each term.
According to the IBM Dictionary of computing, when used to describe disk storage capacity, a megabyte is 1,000,000
bytes in decimal notation. But when the term megabyte is used for real and virtual storage, and channel volume, 2 to
the 20th power or 1,048,576 bytes is the appropriate notation. According to the Microsoft Press Computer Dictionary, a
megabyte means either 1,000,000 bytes or 1,048,576 bytes. According to Eric S. Raymond in The New Hacker's
Dictionary, a megabyte is always 1,048,576 bytes on the argument that bytes should naturally be computed in powers of
two. So which definition do most people conform to?
When referring to a megabyte for disk storage, the hard drive manufacturers use the standard that a megabyte is
1,000,000 bytes. This means that when you buy an 80 Gigabyte Hard drive you will get a total of 80,000,000,000 bytes of
available storage. This is where it gets confusing because Windows uses the 1,048,576 byte rule so when you look at the
Windows drive properties an 80 Gigabyte drive will report a capacity of 74.56 Gigabytes and a 250 Gigabyte drive will
only yield 232 Gigabytes of available storage space. Anybody confused yet? With three accepted definitions, there will
always be some confusion so I will try to simplify the definitions a little.
The 1000 can be replaced with 1024 and still be correct using the other acceptable standards. Both of these standards
are correct depending on what type of storage you are referring.
Processor or Virtual Storage
· 1 Bit = Binary Digit
· 8 Bits = 1 Byte
· 1024 Bytes = 1 Kilobyte
· 1024 Kilobytes = 1 Megabyte
· 1024 Megabytes = 1 Gigabyte
· 1024 Gigabytes = 1 Terabyte
· 1024 Terabytes = 1 Petabyte
· 1024 Petabytes = 1 Exabyte
· 1024 Exabytes = 1 Zettabyte
· 1024 Zettabytes = 1 Yottabyte
· 1024 Yottabytes = 1 Brontobyte
· 1024 Brontobytes = 1 Geopbyte
Disk Storage
· 1 Bit = Binary Digit
· 8 Bits = 1 Byte
· 1000 Bytes = 1 Kilobyte
· 1000 Kilobytes = 1 Megabyte
· 1000 Megabytes = 1 Gigabyte
· 1000 Gigabytes = 1 Terabyte
· 1000 Terabytes = 1 Petabyte
· 1000 Petabytes = 1 Exabyte
· 1000 Exabytes = 1 Zettabyte
· 1000 Zettabytes = 1 Yottabyte
· 1000 Yottabytes = 1 Brontobyte
· 1000 Brontobytes = 1 Geopbyte
Binary Numbers
Information stored in a computer may be thought of as a series of switches, which are either on or off and are indicated
by either the number 0 (off) or the number 1 (on). Computers use the binary number system. In the binary, or base-2,
system of numbers, numbers are formed using the digits 0 and 1. Each place in a binary number is associated with a
power of 2. Binary numbers are written with the subscript two so that they are not confused with numbers in the
decimal system. A digit in the binary system is called a bit, an acronym for binary digit.
Notes on the Binary System
A "bit" (short for "binary digit") is the smallest piece of data that a computer knows. It is a single digit, which can be a
one or a zero. By combining groups of bits and manipulating them, a computer can accomplish all the remarkable things
it has a reputation for doing. Because this grouping of bits is so important, some special names have developed.
A "word" is a group of any number of bits. A "byte" is a group of 8 bits, but it could also be called an "8-bit word".
Everybody knows that a nibble is half of a bite, so in the binary system, a "nibble" is a group of 4 bits, or half of a byte.
Now call each binary digit a "bit." Put 8 bits together to make a byte. If you wrote down all the different possible
combinations of ones and zeros that could make up a byte, you would have 256 different
Example:
Decimal
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Binary
0
1
10
11
100
101
110
111
1000
1001
1010
1011
1100
1101
1110
1111
Binary Place Value
Eights (2³)
Fours (2²)
Twos (2¹)
Ones (2º)
1
1
0
1
You can use the expanded form of 1101two to find the value of the number as a decimal, or base-10, number.
(1·2³)+(1·2²)+(0·2¹)+(1·2º)
So, 1101two = 13ten.
=
(1·8)+(1·4)+(0·2)+(1·1)
=
8+4+0+1
=
13
Binary Worksheet
Name__________________________
Period___________
Example:
1001two
=
=
=
(1·2³)+(0·2²)+(0·2¹)+(1·2º)
8+0+0+1
9
Write each binary number as a decimal number. [Show all steps of your conversion!]
1.
1011two
2.
1100two
3.
10001two
4.
11011two
5.
11111two
6.
100000two
7.
111101two
8.
100011two
Convert these decimal numbers into binary numbers:
9.
23
10.
58
11.
156
12.
235
13.
33
14.
100