Sorry ,
INC(A,x,y):
Increase A[x] by y
NullNumber:
for all x upto Max_Digit , let A[x]=0
SetPosition:
Numbers are added into A[x] from left to write. Return , number's digit.
shownumber:
cout A[x] up to positionflag.
Here is the full-testing program. mult2() function and some of them are for testing ,you can delete them all.