CS2100: Pointers and referencing

Declaration

- The & operator gives the address of a variable

- The *ptr means that ptr is a pointer variable and anything thats assigned to ptr is a mem location

- Memory is integer

Note: Memory is not always consecutive

Usage

Declaring x:
int x;

Declaring pointer:
int *ptr, *ptr2

Point ptr to x's address:
ptr = &x
//*ptr is pointing to the x, ptr contains the address of x

Copying:
ptr2 = ptr
//ptr2 is copying ptr, it has the mem add of x

Dereferencing

We use the * infront of the pointer to manipulate the destination

ie.

ptr = &x 

// ptr contains the mem add of x and points to x

*ptr = 1234 

//we changed the value of x to 1234

ptr = 1234 // ptr is now pointing at the mem address of 1234 not x

Note: using *ptr = &x is wrong!!

Application

scanf("%lf", &input)

// We assign the value into the address &input

We can also use it through function

e.g:

swap_Add(&i,&j);

void swap_Add(int* a, int* b){

  int temp;

  

  temp = *a;

  *a = *b;

  *b  = temp;

}

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