Computer Coding

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Computer Coding Number Systems
?.????????? ?????????????????????????? ?????
3503500 ??? 715E-mail pattamaporn.p_at_bu.ac.thHom
epage http//tulip.bu.ac.th/pattamaporn.p/
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??????????????????????????????

• ?????????????????????????????????????????????????
  ?????????????????? ?????????????????????????
  Binary System

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Binary System
??????????????????????????? Bit (Binary Digit)
?????????????????????????????????????????
???????????????????????????????????
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Bit
?????????????(??? 2) ??????????????? ?????????
one bit
two bits
three bits
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Binary System
?????????????? (??????? 256 ??????)?????Binary
System ??????????????????????????? 0 ??? 1
?????????????????????????????????????????????
(???? ???? ???) ???????????????????????????
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Off/On Switches

• ?????????????????????????????????????????????????
  ????????????????????????????????? (on) ???????
  (off)

or
off
on
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Zero or One?

• ?????????????????? (off) ????????? Bit 0
  ???????? ??????????????? (on) ????????? Bit 1

or
Off (0)
On (1)
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1 0 1 1 0 0 1 0
1 0 0 1 0 0 1 0
1 0 0 1 0 0 1 1
1 1 1 1 1 1 1 1
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Byte

• 8 Bits 1 Byte (1 ??????)
• ???? 0100 0001 A
• 0100 0010 B

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One Character of Data

• ??? 1 Byte ?????????????? ?????? 1 ???
  ???????????
• ???????? (A, B, , a, b, )
• ?????? (0, 1, 2, ) ????
• ?????????????? (!, , _at_, , )

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Examples from the ASCII Text Code
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?????????? (Coding Schemes)

• Extended Binary Coded Decimal Interchange Code
  (EBCDIC???-??-???) ??????????????? 256
  ???????????????????????????????
• American Standard Codes for Information
  Interchange (ASCII) - ?????????????????? PC
• Unicode ???? 16 bit ??? 1 Byte ???????????????
  65536

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Storing Bytes

• ??????????????????? Storage ??????????? Memory
  ??????????? Bytes

1 Kilobyte 210 or 1024 bytes 1 Megabyte 220
or 1,048,576 bytes 1 Gigabyte 230 or
1,073,741,824 bytes
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?? (Computer Word)

• ?????????????????????????????????????????????????
  ?????????????????????????????????????????????
  (Word Length) ???????????

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?????????? (Number Bases)
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Number Bases 10,2,8,16
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????????????????? 2 ???? ??? 10

• ????????????????
• Ex. 10112 ??????????????????????? 10
• (1x23) (0x22) (1x21) (1x20)
• 8 0 2 1
• 11

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????????????????? 2 ???? ??? 10

• ?????????
• 11112
• 101012
• 1011102

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????????????????? 10 ???? ??? 2

• ????????????????????
• Ex. 12 ??????????????????????? 2

20
????????????????? 10 ???? ??? 2

• 2 ) 12
• 2 ) 6 ???????? 0
• 2 ) 3 ???????? 0
• 2 ) 1 ???????? 1
• 0 ???????? 1

???????????????? 11002
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????????????????? 10 ???? ??? 2

• ?????????
• 48
• 100
• 123