Pre-Increment, Pre-Decrement, Post-Increment & Post-Decrement in C

In our context:

Pre means the increment or decrement is done before the statement is executed.

Post means the increment or decrement is done after the statement is executed.

So,

i = ++i + i++ + i-- + ++i;

      (a)     (b)    (c)     (d)

is equivalent to the following set of statements:

i = i+1; (a)

i = i +1; (d)

i = i + i + i + i; (the statement)

i = i + 1; (b)

i = i -1; (c)

Case 1: 

So if initially the value of i was i = 10, then the value of i after the statement is executed will be:

i = 10 + 1;

i = 11 + 1;

i = 12 + 12 + 12 + 12;

i = 48 + 1;

i = 49-1;

Therefore if you use printf("%d", i) after the statement you will get 48 as the answer.

Case 2:

Now consider the case: 

j = ++i + i++ + i-- + ++i;

printf("%d", j);

Then these statements are equivalent to:

i = i+1;

i = i +1;

j = i + i + i + i; (the statement)

i = i + 1;

i = i -1;

printf("%d", j);

Therefore if i is 10 initially, 

i = 10 + 1;

i = 11 + 1;

j = 12 + 12 + 12 + 12;

i = 12 + 1;

i = 13 - 1;

printf("%d", j); will give j = 48. The final value of i in this case is 12.

PS: This logic holds for C and C++. It may differ in Java.