$```$

p $=$ malloc$($n$)$ reserves enough space, in the heap, for n char values; p points at it$.$

$//$ make$\_$str$($ch$,$ n$)$ Return a new array containing a int main$($void$)\{$

$//$ string containing n copies of ch$.$ char $*$str $=$ make$\_$str$(\text{'}$X$\text{'},4)$;

$//$ effects: allocates heap memory $[$caller must free$]//$ TRACE:$2$

char $*$make$\_$str$($char ch$,$ int n$)\{$ assert$(0==$ strcmp$($str$,"$XXXX$"))$;

char $*$p $=$ malloc$($n $+1)$; $//$ allocate n$+1$ chars. $\}$

for $($int i $=0$; i $$ n; $++$i$)//$ write to them.

p$[$i$]=$ ch;

p$[$n$]=\text{'}\backslash 0\text{'}$; $//$ null$-$terminate the string

$//$ TRACE:$1$

return p;

$\}$

$```$

Draw memory diagrams at TRACE:$1$ and TRACE:$2.$