what is the difference between a++ and ++a?

Answer 1

++a is prefix which increases the variables value and the uses the new value in expression.

a++ is posfix which takes the variable value first in the expression and then increase the variable.

E.g. prefix:
int x = 4;
int y = ++x; // y = 5

prosfix:
int x = 4;
int y = x++;// y = 4

Answer 2

Example with arrays;

int numbers[3] = {7, 9, 1};
int i = 0;

cout << numbers[i++] << endl;
// Outputs 7 and now i = 1;

cout << numbers[++i] << endl;
//Outputs 1 and now i = 2;

When postincrementing(i++), i was used as an index of the array and THEN incremented by one.

When preinctementing(++i), i was incremented by one and then used as an index of array.

Answer 3

a++ postponed increment and ++a is prepond increment