I was asked to review a document by my manager at work. I found that at a couple of instances, two spaces after a period was being used. When I told her that, she said that the rule is to use two spaces after a period, not one. I was stumped! Up to this moment in my life I had thought that I was supposed to use one space after a period and there she was, telling me that I was wrong. I asked a co-worker to make sure that I was right and he told me the same thing – use two spaces after a period. Badly in need of sanity check, I Googled, and found my answer.
Typewriters had a single font and all the characters were spaced out evenly. Thus, to mark the separation between sentences more clearly, two spaces were to be used. You will come across the same problem if you use a font that is mono-spaced. However, with computer fonts, they can differentiate between characters input and space them appropriately. So, in the age of computers, we use single space after a period. My manager and my co-worker were not wrong, but they were definitely wrong in telling me that I was making a mistake!