# What's the purpose of an array?

1. Aug 16, 2011

### realism877

I know what an array is and what it does. I'm just having a hard time getting the concpet on how it is useful.

2. Aug 16, 2011

### Greg Bernhardt

3. Aug 17, 2011

### Nylex

They're useful for the simple fact that they allow you to store multiple items. Can you not see situations in which you'd want that? If you've got a load of items, frequently you'll want to do the same thing with each one. Without arrays, you'd have to use a load of separate variables and would probably have a lot of duplicated code. Arrays allow you to use loops, for one thing.

4. Aug 17, 2011

For example, say you took a bunch of measurements, maybe the height of every person in a classroom, so you have a heap of numbers and you want to process them to find the average height. With an array, you might do something like this:

Code (Text):
int arrayLength = 30;
int myArray[arrayLength ]; // an array with 30 "slots", pretend we already put the data in
int total = 0;

for(int i = 0; i < arrayLength; i++)
{
total = total + myArray[i];
}

average = total / arrayLength;
If you used a unique variable for each height measurement you might have to do something like this:

Code (Text):
int height1, height2, height3, height4, height5, height6 .... height30; // 30 variables!

total = height1 + height2 + height3 + height4 .... + height 30; // !!!

average = total / 30;
The solution that uses an array is:

a) compact
b) extensible (making the array larger involves changing 1 number)

The solution that doesn't is:

a) large and cumbersome
b) hard to extend (what if you want another 30 measurements? 30 more variables, and then 30 more operations on those variables)

Arrays are great! There are many more data structures available too, Linked Lists, Hash Tables, Trees, and many more.

5. Aug 17, 2011

### SteamKing

Staff Emeritus
Just like you would manipulate matrices and vectors mathematically, arrays allow us to manipulate matrices and vectors numerically with the aid of computers.

6. Aug 17, 2011

### Staff: Mentor

Using an array, you can store multiple values of the same time, using essentially a single name. The individual items in the array can be distinguished by an index.

7. Aug 17, 2011

### realism877

Thanks, Guys. Appreciate it.

8. Aug 24, 2011

### Jaynte

A text string is also a good example.

The above text i just wrote is an array with characters where array[0] = A, array[1] = "space", array[2] = t. and so on.

9. Aug 24, 2011

### Staff: Mentor

Assuming that we're talking about programming languages that store strings as arrays of characters. That would include C, C++, and several other languages.
array[0] == 'A'
array[1] == ' '
array[2] == 't'
etc.