CIS3355: Business Data Structures
Fall, 2008
 

Arrays:

By definition an array is "a data structure which contains a fixed number of contiguous

 storage elements all of the same data type."

Some of the data types that can be stored are integers, longs, and floats.  For our illustration purposes we will be discussing integers.

In C++ when we store integers, they require 2 bytes per number we store.  For large amounts of information storage in memory, the computer must determine:

	What type of data is being stored?
	Where in memory is there a appropriate section of contiguous RAM?

Say we want to store an array that has the first 9 even numbers, we actually need 20 bytes of storage. That is because we also need 2 bytes for the offset.  If there was 20 bytes of contiguous storage starting at 5000, the data would be listed as:

Variable                            Address                        Decimal Value        

even1                                 5000/5001                    0

even2                                5002/5003                    2

even3                                5004/5005                    4

even4                                5006/5007                    6

even5                                5008/5009                    8

even6                                5010/5011                      10

even7                                5012/5013                     12

even8                                5014/5015                     14

even9                                5016/5017                     16

even10                               5018/5019                     18

The result in RAM would look like the following:

Here are some good Array references:

1. http://www.4duk.com/support/corners/filemaker/arrays.html

2. http://computer.howstuffworks.com/c4.htm

3. http://www.4d.com/docs/CMU/CMU10113.htm

Questions:

1. How many bytes of storage are needed for a float?  ANSWER: 4 Bytes

2. On the offset, is the variable stored always 0? True or False   ANSWER: True