How to change a Do loop to a while loop?

Question

I'm a rookie in the loops. I would like to use a While loop to get a solution like using a Do loop.

Do[Print["a[", i, ",", j, "]=", If[j != 4, i + j, -100]], {i, 1, 4}, {j, 2, 6, 2}]
a[1,2]=3
a[1,4]=-100
a[1,6]=7
a[2,2]=4
a[2,4]=-100
a[2,6]=8
a[3,2]=5
a[3,4]=-100
a[3,6]=9
a[4,2]=6
a[4,4]=-100
a[4,6]=10

I have tried to do something like this but I am not getting the correct result.

i = 1;
j = 1;
While[{{i < 4, j < 7} Print["a[", i, ",", j, "]=", 
  If[j != 4, i + j, -100]]}; {{i++}, {j = j + 2}}]

Answer 1

This produces the same result as your Do loop.

i = 1;
While[i <= 4,
 j = 2;
 While[j < 7,
  Print["a[", i, ",", j, "]=", If[j != 4, i + j, -100]];
  j = j + 2]; i++]