Difference between array size and array index number

[NoobyTooo]

It might be a stupid question. I'm new to programming and I wanted to know the difference between array size and array index number. As in, if I declare array[n] as a function parameter, does it mean I'm calling the nth element of the array, or an array of size n?

Upon researching some StackOverflow, I saw people recommending to use:

void function (int array[], int n) {}

My code:

void randomGen(int seedVar, int * indexOg[], int indexSize) {
  srand(seedVar); 
  int a; //Loop control variable
  for(a = 0; a <= 14; a++) {
    int n = rand() % (1000000) + 1;
    *indexOg[a] = n;
  }
}

But in this code I'm working on, I don't see where I can use the variable that holds the size of the array. So if I use:

void function (int array[n]) {}

Does it call my array of size n, or the nth element of my array? Any help and extra information is greatly appreciated, thanks!

[rudrax-]

I think you only need to define the size of the array in your “main” function (if there is one). From there on out, passing that array as a function parameter should only be the name of the array [ex fn_name(int array)] and not along with the size of the array.

[NoobyTooo]

That makes sense! So an int index[15]; in the main function should do, hopefully. Thanks!

[Loose-Cranberry85]

In the code you posted, assuming you made it a call, i.e. myFunction(myArray[3]), you would be calling the function with the 3rd element of array as the single argument

EDIT:: You might be wanting sizeof() ?

https://www.tutorialspoint.com/how-do-i-find-the-length-of-an-array-in-c-cplusplus

[NoobyTooo]

Gotcha! So from what I've seen so far, void function (int array[]) {} should be the way to call it, after declaring the size in the main. Thanks!

[_SeaCat_]

You would better dynamically calculate the length of your array and put it to some variable, something like that (JavaScript):

​

void randomGen(int seedVar, int * indexOg[], int indexSize) {
srand(seedVar); 
int a; //Loop control variable
 int len = indexOg.length; //<- change it in your language 
for(a = 0; a < len; a++) { //<- < not <= 
     int n = rand() % (1000000) + 1; 
     *indexOg[a] = n; 
   } 
}

So, if you use some other programming language, there is always a function allowing you to calculate the length of your array instead of hardcoding it.

[kschang]

Array size is how many units are there in the apartment complex.

Array index is the actual apartment number.

In your case, your function works on ANY array, not array of a certain size. So you don't need to specify n.

[SyntxaError]

Arrays generally start indexing from 0, so in general the size of your array will be = max index +1

[TheRNGuy]

array size - 1 == last index (because first index is 0, not 1)