Arrays

Array programming is a difficult but important concept. It gets to the nitty-gritty of memory allocation in a computer.

What is an array?
Imagine a carton of eggs. You move the eggs by moving the entire carton, or you can move the eggs one at a time. A carton of eggs is an individual entity that contains items which can also be addressed individually. You have "eggs" and then you have egg #1, egg #2, etc. You buy a dozen eggs at the store in a carton, but when you get home, you open the carton and move them one at a time into the little egg-shaped slots inside the refrigerator.

An array is like a carton of eggs, it's a holding place for something. Without the eggs the carton isn't very important. An array is a holding place in memory for things. What things? Numbers, letters, other arrays. The eggs are the items we put in the array. We move items in and out of an array one at a time just like we move eggs out of a carton one at a time.

Two-Dimentional Arrays as maps and visual grids

Imagine a rough map of the U.S. North East with locations of large cities placed on a gid, it might look like this:
012346
1CHI              BOS
2              NY    
3              DC    
4KC                  
5                      
Chicago is at x = 1, y = 1
Boston is at x = 6, y = 1
New York is at x = 4, y = 2
D.C. is at x = 4, y = 3
Kansas City is at x = 1, y = 4

Let's say we're in New York and we want to go to D.C., we need to go south. In this case we need a change in y and no change in x. x = x + 0 and y = y + 1. Our current location is x=4,y=2. Adding 1 to y would put us at x=4,y=3 the location of D.C.


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