Thread: Pointer

weird numbers such as -8164983 come out...

An uninitialized pointer can point to anywhere, so you will get strange values if you attempt to print them or the values they "point" to. If you attempt to dereference them and get their values without initializing them to point to something, then you might get a crash or a random number or something else, that is illegal.

If you initialize the pointer to point to a new int, but don't initialize the int itself, then what you are doing is technically legal I believe, but you will still get some unknown value because the int is not initialized.

Code:

#include<iostream>

using namespace std;

int 	X = 123  ;
float 	Y = 456.7f ;
double 	Z = 9876.54321;

void D( int N ) 
{
	int d = 4444 ;

	cout << "d" <<" "<< d <<" "<< sizeof(d) <<" " << &d << endl;
	cout << "N" <<" "<< N <<" "<< sizeof(N) <<" " << &N << endl;
}

void C( int N ) 
{
	int c = 4444 ;
	D( N ) ;

	cout << "c" <<" "<< c <<" "<< sizeof(c) <<" " << &c << endl;
	cout << "N" <<" "<< N <<" "<< sizeof(N) <<" " << &N << endl;
}

void B( int N ) 
{
	int b = 4444 ;
	C( N ) ;

	cout << "b" <<" "<< b <<" "<< sizeof(b) <<" " << &b << endl;
	cout << "N" <<" "<< N <<" "<< sizeof(N) <<" " << &N << endl;

}

void A( int N ) 
{
	int a = 4444 ;
	B( N ) ;

	cout << "a" <<" "<< a <<" "<< sizeof(a) <<" " << &a << endl;
	cout << "N" <<" "<< N <<" "<< sizeof(N) <<" " << &N << endl;
}

int main( ) 
{
	cout << "variable, contents, size, adress: " << endl;
	A( 12 ) ;

	int  *p, *q, *r, *s, *t, *u ;
	p = new int ;
	q = new int ;
	r = new int ;
	s = new int ;
	t = new int ;
	u = new int ;

	cout << "X" <<" "<< X <<" "<< sizeof(X) <<" " << &X << endl;
	cout << "Y" <<" "<< Y <<" "<< sizeof(Y) <<" " << &Y << endl;
	cout << "Z" <<" "<< Z <<" "<< sizeof(Z) <<" " << &Z << endl;
	cout << "*p" <<" "<< *p <<" "<< sizeof(*p) <<" " << &p << endl;
	cout << "*q" <<" "<< *q <<" "<< sizeof(*q) <<" " << &q << endl;
	cout << "*r" <<" "<< *r <<" "<< sizeof(*r) <<" " << &r << endl;
	cout << "*s" <<" "<< *s <<" "<< sizeof(*s) <<" " << &s << endl;
	cout << "*t" <<" "<< *t <<" "<< sizeof(*t) <<" " << &t << endl;
	cout << "*u" <<" "<< *u <<" "<< sizeof(*u) <<" " << &u << endl;

	return 0;
}

outputs:

Code:

variable, contents, size, adress:
d 4444 4 0012FDE0
N 12 4 0012FDEC
c 4444 4 0012FE3C
N 12 4 0012FE48
b 4444 4 0012FE98
N 12 4 0012FEA4
a 4444 4 0012FEF4
N 12 4 0012FF00
X 123 4 00476DC0
Y 456.7 4 00476DC4
Z 9876.54 8 00476DC8
*p -842150451 4 0012FF7C
*q -842150451 4 0012FF78
*r -842150451 4 0012FF74
*s -842150451 4 0012FF70
*t -842150451 4 0012FF6C
*u -842150451 4 0012FF68

so lets recap: I had to display each variable, contents, size and adress, donce (i think). When outputtin the contents of my pointers i get -842150451, now is this an illegal content because it doesnt point at anything?

Using the above info, i have to draw a map of the memory:

where does the static memory start and end, and does it climb or desend in terms of location im gunna assume, same for systeme stack, dynamic heap and dymanic memory, and i have to determine the total size of the dynamic memory and static memory. If its impossible, is their a way to estimate about the values?

Thanks guys, big help there!

assignement is due tomorrow, and we've already confirmed hes inconfident, guess il do the best i can!