Variables are integers, so what is the value of the expression (a=2, b=5, a++, b++, a+b)?
a=2，b=5
a++=2
，b++=5
At this moment
a=3，b=6
The difference between a++ and ++a is that a++ assigns the value of A to the whole a++, then A+1, while ++a assigns the value of a+ 1 to the whole A++A.