What value of $c$ will complete the square in the expression below and make the expression a perfect square trinomial? \[ x^{2}+16 x+c \] $c=$ Enter the perfect square trinomial as a squared binomial.

Step 1 ：To complete the square, we need to find a value of $c$ such that the expression $x^{2}+16 x+c$ becomes a perfect square trinomial. A perfect square trinomial is of the form $(x+a)^2 = x^2 + 2ax + a^2$.

Step 2 ：Comparing this with the given expression, we can see that $2a$ is equivalent to $16$. Solving for $a$ gives $a = 8$.

Step 3 ：Therefore, $c$ should be $a^2 = 8^2 = 64$.

Step 4 ：Final Answer: $c = \boxed{64}$