So now we're going to look at some code that reflects our basic understanding of the single dimensional array. This piece of code is to take a bunch of data, in this case a series of grades, the five grades for a student and then see what the student's average is. You can see that this could apply to as large a size array as you want. So first off, we establish the size of the array that must be a constant because when we declare an array this way, it's going to come off the stack and the array must be a constant. So here is grades, they're going to be five of them. Recall that grades of zeros is going to be the first element and then grades of size minus one is going to be the last element. Then this syntax with the curly braces is a way to initialize this aggregate data structure. So just like you can initialize a single variable, you can initialize an array of whatever size by keeping a comma separated list of appropriate constant values for that array. If you don't list five of them, let's say you only listed three, then the last two would have been assumed to be zero. Then this is going to be our summing variable and the reason that it's going to be a double is we want the average to be a floating point number. We don't want a truncation error. i commonly is used as a summation variable. So we don't have to say it, if we could say int index maybe that would be more clear. But generally speaking, i, j, k are used as summation variables. Here is our chief iterative idiom. For i replaced by zero, start with the lowest element of the array. Go up to size, auto-incrementing and do something. This is the step, the internal step of that iteration. In this case, we're going to print the individual grades. We're going to print them separated by tab values. Then we will jump two lines, then we will do this further work of doing a summation of all the grades. Again, size could have been arbitrarily large as long as we had enough data. So this program, this simple program could work for humongous size of aggregate data. Then after we're done, here's our average, sum over size. So let's see that that can be made to work. I already compiled the program, it's going to be in this grade.exe code. Sure enough, my grades are 78, 67, 92, 83, 88. My average is 81.6. So once you have that understanding and you can modify this program, you're nearly a professional coder. Then once you can manage aggregate data of any size especially using the array, you have almost all the tools you need to be a competent programmer.
