The inventor of abc?people have ben using it for decades.

People have been using alphabetic notations for about 3500 years that we know of. Those notations were not ABC. The central innovation in ABC is the header part of the tune - this is an idea derived from TeX and which probably wouldn't have come naturally to anyone living at a time when TeX wasn't around. (The earliest computer implementations of ABC translated it to a macro system built on top of TeX, which in turn generated typeset staff notation).

it is [imo]an inferior system to music notation,and inferior to learning by ear.
it is in my opinion,more difficult to define rhythym accurately than standard music notation,so why bother, why not learn to read music notation,it is not verey difficult,or alternatively record the tunes and learn by ear.

How about you actually look at the ABC website, look at what people do with it, and learn something before talking out of your arse?

Here's my equivalent of Chris's anecdote. I was noodling on an electronic bagpipe on a train in Slovakia and this 2/4 march tune popped out. All I had to record it on was the white space on a used train ticket. Hence the title.

X:1
T:Marion's Ticket
C:Jack Campin 2007
M:2/4
Q:1/4=72
K:Hp
A2A>A B2A2 |e2e>f g4|a2e2 a2e2 |a2e>d B2G2|
A2A>A B2A2 |e2e>f g4|a2e>d B2ed |B2A2 A4 :|
a2e>g a2e>g|a2e>f g4|a2e>f g2e>d|e2d>B B2G2|
A2A>A B2A2 |e2e>f g4|a2e>d B2ed |B2A2 A4 :|

You don't need to know ABC to hear it or see it in staff notation - just copy it (all ten lines) into the box at the folkinfo converter, hit the Submit button and it will generate the staff notation. Click on the staff notation and it will play a MIDI.

Now tell me what more I could have conveyed about that tune if I'd used staff notation instead. I'd have had to write helluva small.