I don't find these results consistent:

OrderedQ[{"a", "A"}]

True

OrderedQ[{"a2", "A1"}]

False

Is there any explanation of that somewhere? (In fact it is not necessarily related to Mathematica, maybe there are some standards or established conventions about this.)

One could think that the explanation is: since "a" and "A" are equivalent
and as OrderedQ[{"A", "A"}] returns True, it's normal. But in that case OrderedQ[{"A", "a"}] shouldn't return False.

###EDIT

(Thanks to @Michael E2 comments)

It turns out that this question has nothing to do with the fact that "1" and "2" are digit characters. The same thing happens if one replaces "1" by "c" and "2" by "d" for example.

###EDIT2

This has been tested on Mathematica 11.3 and 5.1

I don't find these results consistent:

OrderedQ[{"a", "A"}]

True

OrderedQ[{"a2", "A1"}]

False

Is there any explanation of that somewhere? (In fact it is not necessarily related to Mathematica, maybe there are some standards or established conventions about this.)

One could think that the explanation is: since "a" and "A" are equivalent
and as OrderedQ[{"A", "A"}] returns True, it's normal. But in that case OrderedQ[{"A", "a"}] shouldn't return False.

EDIT

(Thanks to @Michael E2 comments)

It turns out that this question has nothing to do with the fact that "1" and "2" are digit characters. The same thing happens if one replaces "1" by "c" and "2" by "d" for example.

EDIT2

This has been tested on Mathematica 11.3 and 5.1

I don't find these results consistent:

OrderedQ[{"a", "A"}]

True

OrderedQ[{"a2", "A1"}]

False

Is there any explanation of that somewhere? (In fact it is not necessarily related to Mathematica, maybe there are some standards or established conventions about this.)

One could think that the explanation is: since "a" and "A" are equivalent
and as OrderedQ[{"A", "A"}] returns True, it's normal. But in that case OrderedQ[{"A", "a"}] shouldn't return False.

###EDIT

(Thanks to @Michael E2 comments)

It turns out that this question has nothing to do with the fact that "1" and "2" are digit characters. The same thing happens if one replaces "1" by "c" and "2" by "d" for example.

I don't find these results consistent:

OrderedQ[{"a", "A"}]

True

OrderedQ[{"a2", "A1"}]

False

Is there any explanation of that somewhere? (In fact it is not necessarily related to Mathematica, maybe there are some standards or established conventions about this.)

One could think that the explanation is: since "a" and "A" are equivalent
and as OrderedQ[{"A", "A"}] returns True, it's normal. But in that case OrderedQ[{"A", "a"}] shouldn't return False.

###EDIT

(Thanks to @Michael E2 comments)

It turns out that this question has nothing to do with the fact that "1" and "2" are digit characters. The same thing happens if one replaces "1" by "c" and "2" by "d" for example.

###EDIT2

This has been tested on Mathematica 11.3 and 5.1