Help me out finding errors

Hey there

I have a homework to calculate the total grade on some quizzes. I know there are some error, could you please help me out finding and fixing them??

A = cell(20,7);
i = 1;
x = input ('Enter the student''s name ( or to termate ):','s');
while(~strcmp(x,'0'))
    A{i,1} = x;
    A{i,2} = input('Enter the grade for the exam 1 ( out of 20) ');
    A{i,3} = input('Enter the grade for the exam 2 ( out of 20) ');
    A{i,4} = input('Enter the grade for the exam 3 ( out of 20) ');
    A{i,5} = input('Enter the grade for the exam 4 ( out of 20) ');
    A{i,6} = A{i,2};
    for j = 2:5
        A{i,6} = A{i,6} + A{i,j};
    end
    z = floor(A{i,6}/10);
    if (z < 6)
        A{i,7} = 'F';
    elseif (z < 7)
        A{i,7} = 'D';
    elseif (z < 8)
        A{i,7} = 'C';
    elseif (z < 9)
        A{i,7} = 'B';
    else (z < 9)
        A{i,7} = 'A';
    end
    x = input ('Enter the student''s name ( or to termate ):','s');
    i = i+1
end

I’m receiving this error!

Enter the grade for the exam 1 ( out of 20) Attempt to execute SCRIPT test as a function: /MATLAB Drive/test.m

Error in HM11 (line 8) A{i,2} = input('Enter the grade for the exam 1 ( out of 20) ');

[Walter Roberson]

A{i,6} = A{i,2};
for j = 2:5
      A{i,6} = A{i,6} + A{i,j};
end

A{i,2} is being counted twice because of the way you initialize. You should initialize to 0.

[Raed Noor]

Thanks, I should add anther input for 20 more points. What about the fptintf ?

[Walter Roberson]

What about the fprintf() ? Your question does not mention fprintf()

fprintf('Student name: "%s", grade: "%s"\n', A{i,1}, A{i,7});

By the way, your code is very trusting that none of the responses will be nan or infinite, and that no-one will have a perfect score...And have a close close look at what you are comparing each value to.

[Raed Noor]

It's my prof's and he want's me to fix it. If it was mine, it'll be way to sampler. I hope it works now. Thank!