A++ and --A

Question

if A++ is like
A = A + 1
then whats --A?

Answer 1

--a is pre decrement. It will decrease value of a by 1.

Answer 2

You have to differentiate between post and pre increment. These 2 have different meanings.
For Pre :
++a // means a=a+1
--a // means a=a-1

For post :
a++ // a=a+1
a-- // a=a-1

The difference between pre and post is the order of execution.
Pre first de/increases its value then continues the normal order.
post first calculates its current calculation with the current value. Then de/increases the variable by one. Then continues with the normal order.