condition in a loop

I have the loop as given below. But I need to restrict the value of b till 30, i.e. the value of b cannot exceed 30. 'a' value does not have a limit. I am not sure how to proceed.

a=0;
b=0;
g=a+b;
while g<100
    a=a+1
    b=b+1
    g=a+b
end

Answer 1

[Birdman]

a=0;
b=0;
g=a+b;
while g<100
   if b<30
      b=b+1
   else
   end
    a=a+1 
    g=a+b
end

[Busy Bee]

Thank you!