could someone please explain this program to me? I'm a beginner in C.

Program #1:
main ()
{
int I;
int a[5] = {39,23,34,12,4};
int b[5];

I = 0;
while (I < 5) {
b[i] = a[4-i];
I=i + 1;
}

I = 0;
while (I<5) {
a[i] = b[i];
I = I + 1;
}
}


Program #2:
main()
{
int a[] = {10,20,30,5,15,25};
int n = 6;
int I, t;

for (I = 0; I < n/2; I+=) {
t = a[i];
a[i] = a[n-i-1];
a[n-i-1] = t;
}
}


Could you please help me understand them, especially what each expression or command line means? Thanks.