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How to Spot a Numeral Zero from a Character O?

Gloria writes:

Is there a way to distinguish between a zero and an “O” when entering a serial number? Sometimes – for various reasons – you receive a serial number that needs to be entered somewhere else, and I can’t tell the difference.

Many of us are confused by the shape of the numeral 0 and the capital ‘o’. If the text is digital, it is easier to identify by changing the font to one that distinctly differentiates between a zero and an ‘O’. However, distinguishing one from the other in printed copies, like serial numbers, is hard at times.

Some History

Most of the time, a check still gets cleared if you type it for $5 followed by two O’s and not zeros, but for those that care, let’s go back in history a bit. The situation used to be much different, once upon a time, when the closest thing we had to a computer was a typewriter. You’d be surprised to know that in the early days, typewriters made no distinction between a zero and an O – so much so, that some typewriters did not even have a separate key for zero.

Modern displays

With the advent of character displays, there came a need to distinguish the two. After all, it was all about typeface, and people love a good font. The digit zero has changed in form twice, once being represented with a slash and another time with a dot in between. However, none of these display styles for zero could strip it of its glory in the battle against ‘O’. So, in modern times, both zero and O have no dot or slash in them. The only thing that has changed is that a computer will not accept an O for a zero!

Distinguishing a zero from an O

The only probable way to distinguish between a zero and an O is to improvise. Most (but not all) fonts try to portray a zero as an oval with a sharp top and bottom and flat sides. If you turn a printed zero sideways, you will clearly see it resting on a flat belly. An O on the other hand, can be perceived as something that is easy to roll.

Here is a list of fonts and how they show a zero an O. As we can see, distinguishing a zero from an O within the same font is easy, but for some fonts, like Georgia, it gets a bit harder. Always remember, a zero will have nearly flat sides and an O will have a broadly rounded top and bottom in most cases.

Zero/o in caps Font Name
0/O  Arial
0/O  Andale Mono
0/O  Georgia
0/O  Book Antiqua
0/O  Times New Roman
0/O   Verdana

~Chinmoy Kanjilal