Simply i mean if i type 2+3=, for example i was trying many ways. I checked did i not use same register or memory location twice but i can't find miss take.
wrong approach, you should decide on "the way" without 'trying', then code and debug "the way".

I took a quick look at your code below and since you have posted it properly I did look quite a bit.

your code is virtually impossible to follow, there are no routine headers and the labels are totally misleading.

examples
KEYTODEC:
should have a header
;enter with key value exits with value equivalent. NOTE - misleading label -it does NOT return 'decimal' per se, it returns the value, which could be considered binary, hexadecimal ....
this is horrific:
CJNE A,#'+',PLUS
it jumps to 'plus' if it is not plus

it is totally confusing and the thing is that - even if you wrote it - it will confuse you too.

Erik