2. Software brings the machine to life
When a computer is using a particular program, it
is said to be running or executing that program.
Two major categories of software
System software, i.e., Operating System
Application software
2345
2554 Real-world tasks Application Useful output
3089 Software
...
System
Software
Hardware
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3. Operating Systems
The operating system tells the computer how to
interact with the user and how to use devices
such as the disk drives, keyboard, and monitor.
The operating system is continue to run until the
computer is turned off.
When a computer is turned on, it goes through
steps to prepare itself to run user's application:
Run system software located in ROM BIOS.
Next, the computer runs the operating system in
diskette, hard disk, or other storage devices.
After the computer finds and runs the operating
system, the user can issue commands to the
computer.
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4. Application software
Application software is a program that help
people accomplish specific tasks.
Thousands of application are available; however
some major categories that likely to be encounter
are:
Word processors
Spreadsheets
Database management software (DBMS)
Multimedia, graphics and presentations
Utilities
Communications
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10. Transforming Data into Information
Computers cannot understand anything about us.
All they can do is recognizing two distinct states produced
by electricity, magnetic polarity, or reflected light.
All they can understand is whether a switch is on or off.
The CPU consists of several million tiny electronic switches
called transistors.
A computer assembling its individual on/off switches into
patterns that are meaningful to us.
In strictest sense, data consists of the raw numbers that
computers organize to produce information.
Computers turn raw, separated data into meaningful
information.
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12. How Computer Represents Data
To a computer, H 0100 1000
everything is a e
r
0110
0111
0101
0010
number. e 0110 0101
0010 0000
For computer, the a 0110 0001
sentence "Here r
e
0111
0110
0010
0101
are some words" 0010 0000
s 0111 0011
is represented by: o 0110 1111
m 0110 1101
e 0110 0101
0010 0000
w 0111 0111
o 0110 1111
r 0111 0010
d 0110 1000
s 0111 0011
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13. Number Bases
A number base is a specific collection of symbols
on which a number system can be built.
The number base familiar to us is base 10, upon
which the decimal number system is built. There
are ten symbols, 0 through 9, used in decimal
system.
When we need to represent a number greater
than 9 we use two symbols together; as 9 + 1 =
10.
Each symbol in a number is called a digit, so 10
is a two-digits number.
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14. Other Number Systems
Binary: Base 2
Octal: Base 8
Hexadecimal: Base 16
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17. Numbers in a computer
In a computer, all data must be reduced to
electrical switches. A switch has only two states
--”ON” or “OFF” -- so it has only two numeric
symbols. 0 stands for “OFF”, and 1 stands for
“ON”.
Computers function in a binary number system
(base 2).
When a computer needs to represent a quantity
greater than 1, it uses the second digit.
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18. Bits and Bytes
When referring to computerized data, each
switch -- whether on or off -- is called bit.
The term bit is a contraction of binary digit.
A bit is the smallest possible unit of data.
To represent anything meaning -- that is to
convey information -- the computer needs groups
of bits.
The larger unit of data is the byte, which is a
group of 8 bits.
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19. (cont'd.)
With one byte, the computer can represent up to
256 different values because it is possible to
count from 0 to 255 with 8 binary digits (one
byte).
One byte combination is an enough unit to
represent all the (English) characters on the
keyboard, including all letters (uppercase and
lowercase), numbers, punctuation marks, and
other symbols.
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20. Character Codes
The programmers need a standard code which is
group of numbers to represent or stand for letters
of the alphabet, punctuation marks, and other
symbols.
ASCII
Unicode
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21. ASCII
The American National Standard Institute (ANSI)
solution to represent the symbols with bits of
data was the ASCII character set.
ASCII = American Standard Code for Information
Interchange
Today ASCII is the most common character set
used.
ASCII is the seven bits code.
The ISO (International Standard Organization)
standard expanded on the ASCII character set,
to offer different sets of characters for different
language group.
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22. (cont'd.)
Dec Hex Code Dec Hex Code Dec Hex Code
32 20 space 48 30 0 68 40 D
33 21 ! 49 31 1 69 41 E
34 22 “ 50 32 2 70 42 F
35 23 # 51 33 3 ..
36 24 $ 52 34 4 90 5A Z
37 25 % 53 35 5 91 5B [
38 26 & 54 36 6 92 5C
39 27 ' 55 37 7 93 5D ]
40 28 ( 56 38 8 94 5E ^
41 29 ) 57 39 9 95 5F _
42 2A * 58 3A : 96 60 `
43 2B + .. 97 61 a
44 2C , 64 40 @ 98 62 b
45 2D - 65 41 A 99 63 c
46 2E . 66 42 B 100 64 d
47 2F / 67 43 C 101 65 e
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23. Unicode
Unicode Worldwide Character Standard
represents each symbol by two bytes --16 bits.
With two bytes, a Unicode character can be any
one of more than 65,536 different characters or
symbols.
Many software publishers, including Microsoft,
Netscape, and Accent, encourage their
developers to use Unicode in their programs.
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24. Users
Job related to computer
Computer engineers
System administrators
Network administrators
System analysts
Programmers
Software testers
System maintainers
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25. (cont'd.)
Many jobs use computer as a tool.
Accountants
Draftsmen
Animators
Data entry worker
Customer support specialists
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26. Responsibility of the users
Keep computer from malicious software
Virus, worm, trojan, spam, internet fraud
Anti virus/spyware
Update software, patches
Recognize limitations of computer systems
Hardware errors ~ design error, hardware failure
Software errors ~ OS, applications
Applying wrong ways
Use computer for working
The Computer Crime Act B.E. 2550
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