pointer A is a variable that stores the address of another variable
=>Provides another way to re fu to a variable, through its address ratger tgab its symbolic
name
-Declaration
int *p;
Setting Pointers:
int a, *p, *g;
p = &a; // & means 'address of int', p is the address of a
g = p; // g has the same address of p
Access through Pointers:
int a, x, y, *p;
p = &a;
x = *p + y; // pointer dereference
*p = x + y;
Memory
---------|
|
|
|
---------0021303 | a
---------|
|
|
|
---------0021323 | p
---------|
|
|
|
----------
| // a is a variable; we make the address p to indicate the location of a;
| // p is the location of a; but p also has a location 'int **p;'
Printing Pointers:
printf("%p", // p); print the thing stored in p
III .pointer arithmetic
Adding a value to a pointer changes the pointer in increments of the sign of the element
being pointed to: (e.g.)
Int a, *p;
Double b, *g;
P = &a;
P = P + 5;
If &a = 0x100, then p = 0x100 + (4*5) = 0x114 //4 is for int, 4 bites
G = &b;
G = g+3;
If &b = 0x200, then p = 0x200 + (8 *3) = 0x218 //8 is for double, 8 bites
P++; => 0x114 + 4 = 0x118
G++; => 0x218 +8 = 0x220
*(a+i) = &a[i]
IV. Pointers and Function Arguments
Int main()
{
Int x = 5;
Foo(x);
}
Void foo (int z)
{
Int y;
Y = z + 10;
Z = 7;
}
Int main()
{
Int x = 5;
Foo(&x);
}
Void foo (int *z) //int * is pointer declaration
{
Int y;
Y =* z + 10;
Z = 7;
}