count the quantity of prime number before my number

Hi, I want to write a code to determine the quantity of prime number before the number selected by the user.

and I want to determine which numbers are prime inside of the loop. can you please help me?

x=input('Input a positive integer, or 0 to quit: ');

a=mod(x,1);

k=x-1;

for c=2:1:k

count=0;

for b=1:1:c

if mod(c,b)==0

count= count+1;

end

end

p=0;

if count==2

p=p+1; % c is prime

end

end

fprintf('count of prime numbers up to %g is: %g ',x,p);

end

Answer 1

[Andrei Bobrov]

x=input('Input a positive integer, or 0 to quit: ');

z = [2,3:2:x];
y= mod(z(:),z(:)');
out = z(all(tril(y) + triu(ones(size(y))),2));