Asst.Prof.Urachart Kokaew

1
????? 9 ?????????????????????????????????????????
Asst.Prof.Urachart Kokaew
2
?????????? (Pointer)

• ?????????? ??? ??????????????????????????????????
  ???? ?????????????????????? machine
  ????????????????????????? type ??????????????????
  ??????????????????????? indirectly
• ???????????????

type var
3
?????????? (Pointer) (???)

• ???? int iptr //?????????????????????????????
  ?? integer
• char cptr //???????????????????????????????
  character

iptr integer var



cptr char var


4
????????????

• ???????? ????????????????????????? 2
  ?????????????????????????? ??????
• ??????? indirect operator
• ?????????????????????????????????????????????????
  ??????????????????????????????????????????????????
  ?
• ??????? address operator
• ??????????????????????????????????????????????
  ????????????????????????????

5
???????????? (???)

• ???????? ????
• char ptr NULL
• ???? declaration ??????????????????????????????
  ????????? ptr ??????????? NULL
• ptr NULL
• ???? executable code ????????? NULL
  ???????????????????????? ptr ?????

6
???????? 1. ???????????????????????

• main()
• int num 3
• int ptr
• ptr num
• printf(The value of num is d.
• Its address is lu.,ptr,(long)ptr)

7
??????????????????

• ???????
• gtThe value of num is 3. Its address is
  448925078.
• ???????? ?????????????????????????????????????????
  ??????????????????

8
???????????????
Declaration int num 3 int ptr num int var ptr
Executable code ptr num num ptr
3

3

9
???????? 2 ???????????????????????

• main()
• static int number6 1,2,3,4,5,6
• int i,ptr
• for(i0ilt6i)
• ptr numberi
• printf(d\n,ptr)

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

• ???????
• 1
• 2
• 3
• 4
• 5
• 6

???????? ???????????? int ptr???????????? ptr
?????????????????????????
ptr
number ???? ptr number0
11
????????????? 2

number
i 0 i 1 i 2 i 3 i 4 i 5

ptr
0 1 2 3 4 5
1
2
3
4
5
6

ptr ptr ptr ptr ptr




12
???????? 3 ?????????????????????????????

• int strlen(s)
• char s
• char p s
• while(p ! \0)
• p
• return (p-s)

13
???????????????????????? 3

• ??????????????????????????????????? string
• ??? string ???????????????????????????????????????
  ???????? string ??????????????????????????????????
  

A B C D E F \0
S

P
?????????????? P-S
14
?????????????????????

• ???????? ????????????????????????????????????????
  ?????????????????????????????????????????????
  ???? int parray10

parray0 parray1 parray2 . . parray9
parray0 parray1 parray2 . . parray9
parray0 parray1 parray2 . . parray9
parray0 parray1 parray2 . . parray9
parray0 parray1 parray2 . . parray9
int.var int.var int.var int.var
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???????? 4 ????????????????????????????

• main()
• int j,n11n22n33ptr,parray4
• parray1 n1
• parray2 n2
• ptr n3
• parray3 ptr
• for(j1jlt4j)
• printf(d\n,parrayj)

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????????????????????????? 4

• ?????????????????????????????????????????? int
  var
• ??????????????????
• 1
• 2
• 3

17
???????????????

• declaration
• int n11,n22,n33,ptr, parray4

• executable code

n1 n2 n3
n1 n2 n3
1 2 3
1 2 3
parray
parray


0 1 2 3 ptr
0 1 2 3 ptr
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???????????????????????????????

• ???????????????????????????????????????????
  ????????????????????????? string
  ?????????????????????? ??????????? string
  ????????????????????????????????
• ??????????????????????????????????????????????????
  ?????????? ??????????????????????????????

19
???????? 5 ???????????????????????????????

• char month(n)
• int n
• static char name
• illegal month,January,
  February,March,April,May,June,July,
  August,September, October,November,
  December
• return((nlt1 ngt12)?name0 namen)

• char month()
• main()
• int num
• puts(Enter number of month)
• scanf(d,num)
• printf(The name of month is s,month(num))

20
????????????????????????? 5

• ???????
• Enter number of month
• gt 6
• The name of month is June

21
???????????????
name0 name1 name2 name12 illegal month
name0 name1 name2 name12 January
name0 name1 name2 name12 February
name0 name1 name2 name12 . .
name0 name1 name2 name12 December
22
Content ??SHEET

• 9.1 ?????????????? Pointer
• 9.2 ????????????? Pointer
• 9.3 ??????????????? Pointer ??? Array
• 9.4 ??????????????? Pointer ??? String
• 9.5 Array ??? Pointer
• 9.6 Pointer ??? Pointer
• 9.7 Pointer ??? ?????????? Structure

23
9.1 ?????????????? Pointer

• ?????????????? Pointer ???????????????????????????
  ?????? ????????????????????????? ??????????????
  ??????
• int pt
• ???????????????? pt ?????????? Pointer ????????
  Address ????????????????????????????

24
????????????? pointer

• ?????????????????????? 2 ?????? pointer ???
• ??????????? ???????? ????????? ??????????????
  Address (Address ??????? ???????????? Pointer
  ??????????????????????? )
• ??????????? ???????? Address ???????????????????
  ????????????? ???????????

25
??????????????????? pointer

• ?????????????????? 2
• ?????????????????? pointer ???????????????????????
  ?????????
• ?????????????????? 3
• "Warning c\prg\Prg08-03.cppSuspicious pointer
  Conversion in function main
• C Error pointer1.cpp(28) E2034 Cannot
  convert 'int ' to 'float '
• ?????????????????? 4
• Null pointer assignment

26
9.2 ????????????? Pointer
    ?????? ,,- ??? -- ??????????????????
???????????? ???? ?? ????????? Pointer ??????????
???????????????????? ???? pt pt60
       pt --     ??????????????????????????
Pointer ?????????????????????????? compiler
??????? byte ???????????????? ????    
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9.2 ????????????? Pointer
??.?????? compiler ???????? ???????????? a
??????? Address 40 ??????????? ptt
?????????????? Pointer pt ?????????? Address 42
(????? 2 Byte) ????????? a ????????????????????
Pointer pt ?????????? Address 44 (????? 4
Byte) (?????????????????????????????5-8)
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9.3 ??????????????? Pointer ??? Array

• Pointer ???????????????????? Array
• (?????? Array ??????)
• ???????????????????? 9 ?????? pt number ???????
  Pointer pt ?????????????????? Array number
  ?????????????????????? Array ?????????????????????
  ??? Address ???????? Pointer ?????????? Pointer
  ????? Address ?????????? ??????????????
• (????????????????????????????? 9-12)

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9.4 ??????????????? Pointer ??? String

• (????????????????????????????? 13-17)
• ????????????????? 13
• ????????? 7 ???????? spt str
• ????? Pointer spt ?????????????????? Array
  String str
• ?????? for ?????????????????????????????????
  Array ?? ???????????????? ????????????????????????
  ????? String null

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9.5 Array ??? Pointer

• (????????????????????????????? 18-19)
• Array ??? Pointer ?????? Address ?????????
  ??????????????????? ??????????????
• Data type pointer namrsize
• ???????????? int iap5
•         Array ??? Pointer iap ?????????? Pointer
  5 ????????????? Address ??????????????????????????
  ?????? ??????????????????? Pointer ?????? 2 ????
  Address ????????? ???????????????? x
  ????????????? iap2 x

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•       ???????????? 18 ???????? pt ???? Array ???
  Pointer ???????????? Pointer 3 ??? ??????????
  Address ????????????????????????? ?????? Pointer
  ?????? Pointer ???????? ??????????????? ???
  Address ??????????????????? Array x
  ??????????????????????????? Array x
  ???????????????? ?????? Array ????

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9.6 Pointer ??? Pointer

•  
• ???????????? 1 Pointer ??? Pointer
•         ?????????? Pointer ??? Pointer
  ?????????????????????? ??? 1 ??? ???? Pointer
  ???? int pt
•         pt ?????????? Pointer ??????????? Address
  ????????? Pointer ????????? Pointer ?????????????
  ?????? Address ????????????????????????? 

(????????????????????????????? 20-21)
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9.7 Pointer ????????????? Structure
??????? ?????????????????? 22 Input data to
structure by pointer 3 Item Code 121 Name
AA Age 12 Code 122 Name BB Age 23 Code
123 Name CC Age 14 Display data from structure
by use pointer -gt 121 AA 12 ..