# Why 01, 02, 03, 04 and not 1, 2, 3, 4?

It seems designers like to add zero to number sequences, like here:

As I understand it, from design perspective, it’s more boxy and comfortable to work with, but from user perspective isn’t it better just to have plain 1, 2, 3, 4?

Is there some history? Who was first to add zero? Is there any other initiative to do it?

• This doesn't apply in this case, but I use leading zeroes in file naming. Because img001 img002 and img011 would, without the extra zeroes, be ordered as img1, img11, img2. Nov 23, 2017 at 0:59

Cons:

• If anything, it slightly impairs readability, as you have to mentally strip out the unnecessary 0.
• We're not as used to reading numbers left-padded with 0s, so it might be somewhat distracting.

Pros:

• It does, however, provide nice balance, as now each value has two digits.
• Perhaps you could argue that, when found within larger ranges, it is easier to compare values, because each number has a tens digit, so the user doesn't have to find where the two numbers "line up" due to an incongruent number of digits.

Bottom line:

IMO, it doesn't seem like the cons are that bad, and the pros don't really add a whole lot, so it seems most likely that it's just an aesthetic decision.

• just to elaborate a little further on the balance bullet: the extra "0" creates left and right alingnment which creates a sense of balance. Nov 23, 2017 at 6:15

Many computer programs will by default use alphabetical sort, rather than numeric, so a range which isn't padded will be presented out of order after sorting, e.g: 1 10 11 12 13 14 15 16 17 18 19 2 20 21 22 23 24 3

I've never seen that happen with a table of contents, I guess because there generally isn't a need to re-sort the order of a TOC (tbh, from memory I've never actually see a TOC with the extra 0s). But it may be a general "best practice" approach being applied by to all number ranges by the designer.