Q. What is the difference between the following 2 C codes?

#include <stdio.h> //Program 1
int main()
{
int d, a = 1, b = 2;
d = a++ + ++b;
printf("%d %d %d", d, a, b);
}

#include <stdio.h> //Program 2
int main()
{
int d, a = 1, b = 2;
d = a++ +++b;
printf("%d %d %d", d, a, b);
}