Reference
Number of data types expressible by bits
21 = 2 types
22 = 4 types
23 = 8 types
24 = 16 types
25 = 32 types
26 = 64 types
27 = 128 types
28 = 256 types
1 bits
2 bits
3 bits
4 bits
5 bits
6 bits
7 bits
8 bits
(1)Bits and bytes
A “bit” is the smallest unit of data which can be handled by a computer. In
the same way as a binary number, “one bit (also written as “1 bit” or “1
b”)” is represented by either “0” or “1.” Eight bits together can be displayed as “one byte (also written as “1 Byte” or “1 B”).”
00000000
00000001
00000010
28 indicates that 256 kinds of data can be expressed.
11111110
11111111
_
_
1 bit
8 bits = 1 byte
Reference
Prefixes
“Prefixes” are letters used to represent
the size of bits and bytes. These include
K ( kilo ) , M ( mega ) , and G ( giga ) . Although not used independently, prefixes
are used with other units to express the
multiple of 10 applied to that particular
unit.
Prefixes
Long form
Power
K
kilo
3
M
mega
6
G
giga
9
T
tera
12
P
peta
15
(2)Units representing volume of information
Units used to describe information larger than a byte are summarized below.
Unit
Long form
KB
kilobyte
Explanation
MB
megabyte
220 = 1024 KBytes
GB
gigabyte
230 = 1024 MBytes
TB
terabyte
240 = 1024 GBytes
PB
petabyte
250 = 1024 TBytes
210 = 1024 Bytes
* When displaying memory capacity, units are generally converted using “210” as a
multiplier. Normally, a lower case “k” is written if “1000” is the multiplier, while
an upper case “K” is used if “210” is the multiplier.
(3)Units representing time
To denote computer processing speed, the following units are used to represent times shorter than one second.
Unit
2
Long form
ms
millisecond
μs
microsecond
ns
nanosecond
ps
picosecond
Explanation
1
1ms=10 s = 103 s
1
−6
1μs=10 s = 106 s
1
−9
1ns=10 s = 109 s
1
−12
1ps=10 s = 1012 s
−3
Digitization
In order to manipulate “analog data” such as text, forms, photos, and pictures on a computer, converting it into digital code (ranging from “0” to
“1”) or “digitization,” is necessary. Throug h digitization, image processing, copying, communications, and other functions can be executed at high
speeds, greatly expanding the application of data.
In addition, the use of digital data protects the original analog data from
deterioration, allowing for more efficient data utilization.
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