9. pointer
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![9
Pointer Declaration and Assignment
[Ex] int *p;
int month=3;
p = &month;
pointer variable p
month memory address襯 assign
p month
3
p
1000
month
31000
譯殊襯 讌 蟆覲企る
危襯 伎 .
則 Example](https://image.slidesharecdn.com/9-140406045928-phpapp01/85/9-pointer-9-320.jpg)
![10
Addressing and Dereferencing
[Ex] int a, b;
int *p;
a = 7;
b = 7;
p = &a;
printf(*p = %dn, *p);
*p = 3;
printf(a = %dn, a);
p a襯 pointing覩襦, *p == 7
p a address襯 ロ螻
朱襦, *p a襯 覩誤螻,
蟆郁記 a 伎 3朱 覲蟆
p a memory address襯 assign
*p = 7
a = 3
則 Example](https://image.slidesharecdn.com/9-140406045928-phpapp01/85/9-pointer-10-320.jpg)
![11
Addressing and Dereferencing
[Ex1] int a, b;
int *p;
a = b = 7;
p = &a;
*p = 3;
p = &b;
*p = 2 * *p a;
pa
7
b
7
p
3
a b
7
pa
3 11
b
則 Example](https://image.slidesharecdn.com/9-140406045928-phpapp01/85/9-pointer-11-320.jpg)
![12
Addressing and Dereferencing
[Ex1] int x, *p;
x = 10;
*p = x;
[Ex3] int x, *p;
x = 10;
p = x;
Error!!
p 螳 譯殊伎讌 p螳 企 螻褐
refer螻 讌襯 覈襯企
p螳 point 螻褐 x螳 覿螳
Error!!
p address襯 螳朱 point
variable企襦 int assign 覿螳
則 蠍](https://image.slidesharecdn.com/9-140406045928-phpapp01/85/9-pointer-12-320.jpg)
![則 Example
18
Pointer Declaration and Assignment
[Ex] int i = 3;
int *p ;
int **q ;
p = &i ;
q = &p ;
p i
3
i
31000
p
10002000
q
20003000
q](https://image.slidesharecdn.com/9-140406045928-phpapp01/85/9-pointer-18-320.jpg)
![則 Example:
螳 螻 覃覈襴 襯 蠏碁殊
襦 蠏碁Μ.
豕譬朱, i, j 覲 螳 朱
瑚?
i, j, p, q 譯殊襯 螳螳 1000,
1004, 2000, 3000 企朱, p, q, r
螳 螳螳 朱瑚?
19
Pointer Declaration and Assignment
[Ex] int i = 3, j = 2;
int *p, *q ;
int **r ;
p = &i ;
q = &j ;
r = &p ;
*p = 4 ;
*q = 5 ;
**r = 6 ;
*r = &q ;
q =&i ;
**r = 7 ;](https://image.slidesharecdn.com/9-140406045928-phpapp01/85/9-pointer-19-320.jpg)
9. pointer
- 1. Pointer
- 2. 2 Pointer Declaration and Assignment 則 Variables and address 覃覈襴 蟲譟 螳 覲 覃覈襴 轟 譯殊 豺 覲 譯殊: Pointer 1000 a 1001 3.2 1005 4 ch, 1byte f, 4bytes i, 4bytes char ch = a ; float f = 3.2 ; int i = 4 ; address
- 3. 3 Pointer Declaration and Assignment 則 Variables and address 覲覿 覲 譯殊(Pointer) 詞企願鍵 char ch = a ; float f = 3.2 ; int i = 4 ; printf( %d %d %dn, &a, &f, &i ) ; &(覲企) == 覲 譯殊 1000 a 1001 3.2 1005 4 Address operator
- 4. 4 Pointer Declaration and Assignment 則 Variables and address 覲 譯殊(Pointer)襯 伎 覲 蠏狩蠍 char ch ; float f ; int i ; *(&ch) = a ; *(&f) = 3.2 ; *(&i) = 4 ; *(譯殊) (譯殊) 豺 覲襯 詩 1000 a 1001 3.2 1005 4 char ch ; float f ; int i ; ch = a ; f = 3.2 ; i = 4 ; Indirect operator
- 5. 5 Pointer Declaration and Assignment 則 Pointer Variable 覲 譯殊(Pointer)襯 螳 ロ 覲 char ch = a ; float f = 3.2 ; int i = 4 ; char *pch ; float *pf ; int *pi ; pch = &ch ; pf = &f ; pi = &i ; printf( %d %d %dn, pch, pf, pi ) ; data_type * pointer_varaible; char 覲 譯殊襷 ロ 覲 float 覲 譯殊襷 ロ 覲 int 覲 譯殊襷 ロ 覲 char *pch = &ch ; float *pf = &f ; int *pi = &i ;
- 6. 6 Pointer Declaration and Assignment 則 Pointer Variable char ch ; float f ; int i ; ch = a ; f = 3.2 ; i = 4 ; char ch ; float f ; int i ; char *pch = &ch ; float *pf = &f ; int *pi = &i ; *pch = a ; *pf = 3.2 ; *pi = 4 ; 1000 a 1001 3.2 1005 4
- 7. 7 Pointer Declaration and Assignment 則 Pointer Variable 覈 pointer 覲 4 bytes 蠍一企 (4 bytes machine) why?? char *pch ; float *pf ; int *pi ; printf( %dn, sizeof(pch) ) ; printf( %dn, sizeof(pf) ) ; printf( %dn, sizeof(pi) ) ; int i = 0 ; int *pi = & i; printf( %dn, i ) ; printf( %dn, *pi ) ; printf( %dn, &pi ) ;
- 8. 8 Pointer Declaration and Assignment 則 Pointer Variable 覈 pointer 覲 覲企襦 譯殊襯 螳. int i = 0 ; int *pi = &i; printf( %dn, i ) ; printf( %dn, *pi ) ; printf( %dn, &pi ) ; 1000 1020 pi, 4 bytes i, 4 bytes
- 9. 9 Pointer Declaration and Assignment [Ex] int *p; int month=3; p = &month; pointer variable p month memory address襯 assign p month 3 p 1000 month 31000 譯殊襯 讌 蟆覲企る 危襯 伎 . 則 Example
- 10. 10 Addressing and Dereferencing [Ex] int a, b; int *p; a = 7; b = 7; p = &a; printf(*p = %dn, *p); *p = 3; printf(a = %dn, a); p a襯 pointing覩襦, *p == 7 p a address襯 ロ螻 朱襦, *p a襯 覩誤螻, 蟆郁記 a 伎 3朱 覲蟆 p a memory address襯 assign *p = 7 a = 3 則 Example
- 11. 11 Addressing and Dereferencing [Ex1] int a, b; int *p; a = b = 7; p = &a; *p = 3; p = &b; *p = 2 * *p a; pa 7 b 7 p 3 a b 7 pa 3 11 b 則 Example
- 12. 12 Addressing and Dereferencing [Ex1] int x, *p; x = 10; *p = x; [Ex3] int x, *p; x = 10; p = x; Error!! p 螳 譯殊伎讌 p螳 企 螻褐 refer螻 讌襯 覈襯企 p螳 point 螻褐 x螳 覿螳 Error!! p address襯 螳朱 point variable企襦 int assign 覿螳 則 蠍
- 13. 13 const Pointer 覲 則 const Pointer 覲 p const int 覲 譯殊襯 ロ 誤 覲 a 覲襦 螳 覦蠖 . p螳 螳襯危る 覲 覲企襦 p襯 牛 覲蟆暑螳 const int a = 7; const int *p = &a; // 螳 a = 8 ; //覿螳 *p = 9 ; //覿螳
- 14. 14 const Pointer 覲 則 const Pointer 覲 p const int 覲 譯殊襯 ロ 誤 覲 讌襷, 朱 int 覲 譯殊襯 ロ . a 朱 覲襦 螳 覦蠖 . p螳 螳襯危る 覲螳 朱覲願鍵 , p螳 const int 誤磯 碁朱襦, p襯 牛 覲蟆暑螳 int a = 7; const int *p = &a; // 螳 a = 8 ; //螳 *p = 9 ; //覿螳
- 15. 15 const Pointer 覲 則 const Pointer 覲 p 朱 int 覲 譯殊襯 ロ 誤 覲企 襦, 覲 a 譯殊襯 ロ . 襷 願 る *p=8 螳ロ螻 蟆郁記 a 螳 覦蠖 蟆 . const int a = 7; int *p = &a; // 覿螳
- 16. 16 const Pointer 覲 則 const Pointer 覲 p const int 覲 譯殊襯 ロ 誤 覲 覩襦 覈 螳 p const int 覲 譯殊襯 ロ 覲企襦, 豌 豐蠍壱 螳ロ讌襷, 蠏 危 豺 覿螳 const int a = 7, b = 8 ; const int * p = &a; // 螳 p = &b; //螳 const int a = 7, b = 8 ; const int * const p = &a; // 螳 p = &b; // 覿螳
- 17. 17 れ Pointer 覲 則 れ Pointer 覲 i int 覲 p int 覲 譯殊襯 ロ 誤 覲 q int 覲 譯殊襯 ロ 誤 覲 譯殊襯 誤 覲 q 誤磯願鍵 覓語 蠍磯 4覦危語企(4 bytes machine) int i = 4 ; int *p ; int **q ;
- 18. 則 Example 18 Pointer Declaration and Assignment [Ex] int i = 3; int *p ; int **q ; p = &i ; q = &p ; p i 3 i 31000 p 10002000 q 20003000 q
- 19. 則 Example: 螳 螻 覃覈襴 襯 蠏碁殊 襦 蠏碁Μ. 豕譬朱, i, j 覲 螳 朱 瑚? i, j, p, q 譯殊襯 螳螳 1000, 1004, 2000, 3000 企朱, p, q, r 螳 螳螳 朱瑚? 19 Pointer Declaration and Assignment [Ex] int i = 3, j = 2; int *p, *q ; int **r ; p = &i ; q = &j ; r = &p ; *p = 4 ; *q = 5 ; **r = 6 ; *r = &q ; q =&i ; **r = 7 ;