I should have worded this a little better. I also use two spaces after a question mark and exclamation point. Sorry about the confusion in my first comment.
Back in the days when we were all using typewriters it was preferred practice to us two spaces. Now that we have computers with their advanced fonts, a single space is preferred/
Typewriters used a standard size for every letter.
I was always taught to put one
Only one but many times before I didn't even put any space between the dot and first letter.
Two spaces
I prefer one space.
Generally speaking, I use two spaces after a period and one space after a comma, colon, semi-colon, and other forms of punctuation.
I should have worded this a little better. I also use two spaces after a question mark and exclamation point. Sorry about the confusion in my first comment.
I only used to leave a single space after a period.
Back in the days when we were all using typewriters it was preferred practice to us two spaces. Now that we have computers with their advanced fonts, a single space is preferred/
Typewriters used a standard size for every letter.
Computers use proportional spacing.