t

1. Pointers and Addresses
int x;
x=23;
FF00 x
23
Direct reference

2. Pointer Variables
int x=23;
int *x_pointer;
x_pointer=&x;
FF00 x
23
FFF0 x_pointer
FF00
Indirect reference

3. Pointer Variable Declarations
type-name * pointer-variable-name;
int *x_pointer;
int *x_pointer, *y_pointer;
char *charPtr;

4. Pointer Operators
&（address operator）
• Returns address of operand
int y, *yPtr;
y = 5;
yPtr = &y;
5
yPtr
fff0
y
ff00
yPtr
y
5
Address of y is
value of yPtr
yPtr “points to” y
ff00

5. Pointer Operators
*（indirective operator）
• Returns a alias of what its operand points to
• *yPtr returns y (because yPtr points to y)
int y=5, *yPtr;
yPtr = &y;
int y, *yPtr;
yPtr = &y;
*yPtr = 5;

6. Example: Pointer Operators
Example: Pointer operators
#include <stdio.h>
void main() {
int a, *aPtr;
a = 7;
aPtr = &a;
printf("The address of a is %p"
"nThe value of aPtr is %p", &a, aPtr);
printf("nnThe value of a is %d"
"nThe value of *aPtr is %d", a, *aPtr);
printf("nnShowing that * and & are inverses of each other."
"n&*aPtr = %p"
"n*&aPtr = %p", &*aPtr, *&aPtr);
}

7. Example: Pointer Operators
Example: Pointer operators
The address of a is 1A58
The value of aPtr is 1A58
The value of a is 7
The value of *aPtr is 7
Showing that * and & are inverses of each other.
&*aPtr = 1A58
*&aPtr = 1A58

8. Example: Pointer Arguments
Example: call by value
#include <stdio.h>
int callByValue(int);
void main() {
int number = 5;
printf("The original value of number is %d", number);
number = callByValue(number);
printf("nThe new value of number is %d", number);
}
int callByValue(int n) {
return n*n*n;
}
The original value of number is 5
The new value of number is 125