I Love Arrays

1
I Love Arrays

• Someday youll learn to love them too

2
What is an array?

• An array is a group of memory locations with the
  same name and same type
• Arrays contain multiple elements of the same data
  type (int, char, float, double)
• Arrays DO NOT mix different types of data
• Structures can mix types, but youll learn about
  those in later courses

3
Array Indexing
53
c0
2

• Elements of an array are referred to by their
  subscript or index
• This index is contained in the brackets after the
  array name
• In C, the first element of an array has an index
  of 0, the second has index of 1, etc.

c1
-35
c2
1024
c3
0
c4
1
c5
-562
c6
-3
c7
1024
c8
4
Array Indexing
53
c0
2

• WARNING!
• An n-element array will only have an index up to
  n-1
• This is a common source of errors

c1
-35
c2
1024
c3
0
c4
1
c5
-562
c6
-3
c7
1024
c8
5
Array Indexing

• Expressions can be used to evaluate the index
• Example if a 2, and b 3, then
• cab 2 is perfectly valid
• Other okay expressions
• printf(d, c0c1)
• x c5 / 2

6
Defining Arrays

• A twelve element array would be defined with the
  following code
• int c12
• Two arrays of the same type can be defined in the
  same line
• int c12, d256

7
Initializing Arrays

• After defining an array, it must still be
  initialized
• There are many ways to initialize an array
• The most direct way is to use an initializer list
• int n5 56, 23, 1, 0, 8

8
Initializing Arrays

• If the initializer list has fewer elements than
  defined by the array, the rest of the elements
  will be assigned as zero
• That means then that you can initialize an array
  to have all zero values with the code
• int g16 0

9
Initializing Arrays

• Initializer lists can also be used without first
  defining the array
• int g 1, 2, 3, 4, 5
• In this case, the number of elements in the array
  will then be the same as the number of elements
  in the initializer list

10
Initializing Arrays
0
c0
1
c1

• Arrays can also be initialized with more complex
  code

4
c2
9
c3
16
c4
int c9 for (int i 0 i lt 9 i) ci
ii
25
c5
36
c6
49
c7
64
c8
11
Working with Arrays

• Why do I love arrays?
• Because I love digital music, photos, and movies
• Digital music is stored as 1-D arrays an
• Digital images are stored as 2-D arrays amn
• Digital movies are stored as 3-D
  arrays amnt

12
Working with Arrays

• Later on in this course we could use Matlab to
  start programming with sound and images
• For now, well keep things simple with C
• Examples
• survey.c
• dice.c