A question about "Old Irish"?

Question

If in Old Irish, the letter H didn't exist, but was introduced to get over the problem of typewriters not having letters with dots over them (eg ḃfuil becoming bhfuil and maiṫ becoming maith), how would things such as "Dé h'Aoine" or "?????? na hÉireann" have been written?

Answer 1

Old Irish did have the letter H. It consisited of the same 18 letters that modern Irish has.