Yes. As i understand it's something about card game, these calculations are likely used for generating some random numbers. The % operator gives the remainder, so i % 13 always gives a number from 0 to 12, if i is positive, no matter what value i has. The << operator increases the number by shifting it left by one binary place, which means that << 1 is the same as multiplying by 2, << 2 the same as multiplying by 4, but a left shift is much faster than multiplying. What this gives is a random number which changes by a certain bigger unit, say by 4, which is sometimes necessary for a certain random behaviour. And then, i += i / 13 is just the same as i = i + i / 13...

actually i cant understand the logic behind this function
is it like creating a memory space for 52 cards so we can deal with it later or just creating cards...
because there is 2 other functions that show you the deck, shuffle the deck and print the deck again(shuffled).

for (i = 0; i < 52; i++)
{
deck[i] = (i % 13)<<2;
deck[i] += i / 13;
if(i/13 < 2)
deck[i] += 64;
}

Actually, I don't understand it, either. The shifting and adding 64 makes no sense.

Since a deck has 52 cards, the loop is going through all the possible cards of the deck (0-51). Then (i / 13) gives you 0-4, representing the suit of the given card. (i % 13) gives the value or rank of the card (0-12). Therefore, if i is 5 you get the 6 of Hearts.

If you want to shuffle the deck, you can then yse the random generator to move cards to different random positions.

So here is my problem laid out as simple as I can put it.
I cant combine multiple entities together that have related data but are different
(one database table ...