![5/31/2014
• pa = a; instead of pa = &a[0]
• a[i] can be written as *(pa + i).](https://image.slidesharecdn.com/pointers-160831115942/85/Pointers-12-320.jpg)
![5/31/2014
• When an array is passed to a function what is
actually passed is its initial elements location in
memory
• strlen(s) strlen(&s[0])
• This is why we declare the function:
• int strlen(char s[]);
• An equivalent declaration is : int strlen(char *s);](https://image.slidesharecdn.com/pointers-160831115942/85/Pointers-13-320.jpg)
![• We can have arrays of pointers since pointers
are variables.
• Arrays can contain pointers
• For example: an array of strings
• Name array has a fixed size, but strings can be
of any size.
char *name[3] = { “rajan”, “sonu”, “hari”};
‘r’ ‘a’ ‘j’ ‘a’ ‘n’ ‘’
‘s’ ‘o’ ‘n’ ‘u’ ‘0’
‘h’ ‘a’ ‘r’ ‘i’ ‘0’
•
•
•
name[0]
name[1]
name[2]
14](https://image.slidesharecdn.com/pointers-160831115942/85/Pointers-14-320.jpg)
![• Two-dimensional numeric arrays
• int nums[2][3] = {{16,18,20},{25,26,27}};
Pointer Notation Array Notation Value
*(*nums) nums[ 0 ] [ 0 ] 16
*(*nums + 1) nums [ 0 ] [ 1 ] 18
*(*nums + 2) nums [ 0 ] [ 2 ] 20
*(*(nums + 1)) nums [ 1 ] [ 0 ] 25
*(*(nums + 1) +1) nums [ 1 ] [ 1 ] 26
*(*(nums + 1) +2) nums [ 1 ] [ 2 ] 27](https://image.slidesharecdn.com/pointers-160831115942/85/Pointers-15-320.jpg)
Pointers
- 2. 5/31/2014 • Introduction • Arithmetic on a pointer • Pointers and Functions • Pointers and Arrays • Arrays of Pointers • Advanced Pointer Notation
- 3. –Contains memory address as their values. –Normal variable contains a specific value. –Pointers contain address of a variable. –We can have a pointer to any variable type.
- 4. 5/31/2014 • The unary or monadic operator & gives the ``address of a variable'‘ • The indirection or dereference operator * gives the ``contents of an object pointed to by a pointer''. Indirection Operator *
- 5. 5/31/2014 1.We must associate a pointer to a particular Data type 2.Data type of pointer variable & variable must be same 3.Help us to know How many bytes of data is stored in? int i=1,*ip; // pointer Declaration ip=&i;//Pointer Assignment *ip=3;//Pointer Assignment
- 6. 5/31/2014
- 7. When a pointer is declared it does not point anywhere. You must set it to point somewhere before you use it 5/31/2014
- 8. Pointer Arithmetic • Operations are meaningless unless performed on an array. • An arithmetic operator increases and decreases its contents by the size of the data type it points to it • When we increment a pointer we increase pointer by one ``block'' memory
- 9. • Call by value – Pass the value of the variable to the function. x void main() { int = 10; print(x); printf(“n%d”,x); } x)void print(inta a += 10; printf(“%d”,a); } 10 120 20 10
- 10. • Do not pass a variable. • Pass address of variable using & operator. • Allows you to change the value directly at memory location. • Arrays are not passed with & because the array name is already a pointer. print(x); print(&x);
- 11. • Call by reference – Pass the address of the variable to the function. x void main() { int = 10; prin(&x); printf(“n%d”,x); } void prin(int *y) { *y += 10; printf(“%d”,x); } &x 120 20 20
- 12. 5/31/2014 • pa = a; instead of pa = &a[0] • a[i] can be written as *(pa + i).
- 13. 5/31/2014 • When an array is passed to a function what is actually passed is its initial elements location in memory • strlen(s) strlen(&s[0]) • This is why we declare the function: • int strlen(char s[]); • An equivalent declaration is : int strlen(char *s);
- 14. • We can have arrays of pointers since pointers are variables. • Arrays can contain pointers • For example: an array of strings • Name array has a fixed size, but strings can be of any size. char *name[3] = { “rajan”, “sonu”, “hari”}; ‘r’ ‘a’ ‘j’ ‘a’ ‘n’ ‘’ ‘s’ ‘o’ ‘n’ ‘u’ ‘0’ ‘h’ ‘a’ ‘r’ ‘i’ ‘0’ • • • name[0] name[1] name[2] 14
- 15. • Two-dimensional numeric arrays • int nums[2][3] = {{16,18,20},{25,26,27}}; Pointer Notation Array Notation Value *(*nums) nums[ 0 ] [ 0 ] 16 *(*nums + 1) nums [ 0 ] [ 1 ] 18 *(*nums + 2) nums [ 0 ] [ 2 ] 20 *(*(nums + 1)) nums [ 1 ] [ 0 ] 25 *(*(nums + 1) +1) nums [ 1 ] [ 1 ] 26 *(*(nums + 1) +2) nums [ 1 ] [ 2 ] 27
- 16. 5/31/2014