It is good programming style to always use a for loop when the number of times to repeat the action is known. The following code uses a while loop that mimics what a for loop should do. Rewrite it using a for loop that accomplishes exactly the same thing.
 myprod = 1;
 i = 1;
 while i <= 4
 num = input('Enter a number: ');
 myprod = myprod ⁎ num;
 i = i + 1;
 end