The purpose of the following program is to create four threads, indexed as $0,1,2,3,$

and have each thread print its own index. Explain what this program prints. Will it

always print the same text? Explain in detail why or why not. The use of variable ptr has

a very specific purpose. What problem is the programmer trying to solve by using

variable ptr$?$ Has he succeeded? Explain in detail why or why not.

#include "csapp.h$"$

#define N $4$

void $*$thread $($void $*$vargp$)$;

int main$()$

$\{$

pthread$\_$t tid$[$N$]$;

int $i,{?}^{***}$ ptr;

for $(i++==ii=0i++=\%\frac{d}{?}$

$i$; $i++i=0$;$i$; $i++$