C++ post increment usage

gistfile1.cpp

int sum_elements(int[] array, int numOfElements)
{
    int sum = 0;
    int index = 0;
    
    while(index < numOfElements)
        sum += array[index++];
    
    return sum;
}

gistfile2.cpp

int a=5;
int b;
b = a++;

b = a++;

gistfile3.cpp

b = a;
a = a + 1;

gistfile4.cpp

a = a+1;
b = a;

gistfile5.cpp

x = x+1;
x += 1;
++x;

gistfile6.cpp

sum = sum + array[index];
index = index + 1;

gistfile7.cpp

int n = 0;

while(n++ < 10)
    cout << "Number of execution: " << n << endl;

gistfile8.cpp

int n=0;

while(n<10){
    n=n+1;
    cout << "Number of execution: " << n << endl;
}