The following are different programs that implement pointers. What would be the result of

each $?$ Explain in details the concept of each line of below codes.

$1$ #include

using namespace std;

int main$()$

$\{//$Assume that the address of the variable a $=0015$FAA$0$

int a;

int $*$aPtr;

a $=7$;

aPtr $=$ &a;

cout $<<$ &a $<<$ endl;

cout $<<$ aPtr $<<$ endl;

cout $<<$ a $<<$ endl;

cout $<<*$aPtr $<<$ endl;

cout $<<$ &$*$aPtr $<<$ endl;

cout $<<*$&aPtr $<<$ endl;

return $0$;$\}$

$2$ #include

using namespace std;

int main $()$

$\{$ int num$1,$ num$2$;

int $*$mypointer;

mypointer $=$ &num$1$;

$*$mypointer $=10$;

mypointer $=$ &num$2$;

$*$mypointer $=20$;

cout $<<$ "firstvalue is $"<<$ num$1<<$ endl;

cout $<<$ "secondvalue is $"<<$ num$2<<$ endl;

return $0$;$\}$

$3$ #include

using namespace std;

int main $()$

$\{$

int firstvalue $=5,$ secondvalue $=15$;

int $*$p$1,*$p$2$;

p$1=$ &firstvalue;

p$2=$ &secondvalue;

$*$p$1=10$;

$*$p$2=*$p$1$;

p$1=$ p$2$;

$*$p$1=20$;

cout $<<$ "firstvalue is $"<<$ firstvalue $<<$ endl;

cout $<<$ "secondvalue is $"<<$ secondvalue $<<$ endl;

return $0$;

$\}$

$4$ #include

using namespace std;

void double$\_$it$\_1($int $*$p$)$

$\{$

$*$p $=*$p $*2$;

$\}$

void double$\_$it$\_2($int n$)$

$\{$

n $=$ n$*2$;

$\}$

int main$()\{$

int var $=10$;

int $*$pvar $=$ &var;

cout $<<*$pvar $<$