There is no 1-to-1 correspondence to the C++ do while loop in MATLAB. Your best option is to use a while loop. The difference is that while loops check the condition at the beginning of the loop while do while loops check the condition at the end of the loop. while (abs(A-B) <= 50) ... end To check the condition at the end of the loop using a while loop, use an if statement inside the while loop: while 1 if ~(abs(A - B) <= 50) break; end end

I don't really understand your question. Is there a specific thing you would like help with? For direction, I would start reading up on Matlab's for loop and while loop documentation and look at some examples. Remember, for loops step through an iterative process where you define the end step. While loops iterate until a condition is met.

You're saying loop while |ea| is smaller than |es| *OR* |iter| is smaller than |imax|. The first part is always true so it'll keep on looping. You want to loop while *both* are true. This is an *AND*: while ea <= es && iter <= imax

The FOR loop is _nicer_ and more compact, if the number of iterations is known before the loop is started. The WHILE loop is _nicer_, when the number of iterations is determined inside the loop. Compare: for k = 1:10 disp(k); end with: k = 1; while k <= 10 disp(k); k = k + 1; end On the other hand: a = 1e6; while a > 1 a = a * rand; end with this (1e8 is an arbitrary large guess - a bad idea!): a = 1e6; for k = 1:1e8 % Ugly, although it is not created explicitly a = a * rand; if a <= 1 break; end end There are some overlaps, e.g. running an iteration until a certain number of loops or a specific criterion is reached. Then usually WHILE is preferred with the convergence limit as test, because this reflects the main character of the loop, while the limitation of iterations is a fallback mechanism only.

You need to exit your while loop when sum_val > 999. If you look at your exit condition and read it as words, you can see your problem:

while sum_val > 999 is "Loop and perform loop statements while the value of sum is greater than 999".

Since your sum starts at 0, you will never enter your loop, because sum is less than 999. You want:

"Loop and perform loop statements while the value of sum is less than 999"

which is:

while sum_val < 999

As well as this you don't define your counter n. You do this:

sum_val=1+n

When you count your sum, you need to ensure that you are actually summing the right things. What is sum it is the previous value of sum added with the current value of n. So do that:

sum_val = sum_val + n

Also what is n? Well as in the problem statement, n counts from 1 to N (your eventual goal). So you need to make sure you update that (and set it).

n = 1
...
n = n+1

Finally, sum is a function name, so you cant use it. Use something else, like sum_val as shown above.

You will need to sort out where in the code these should go.