1. Arrays are structured data types that allow storing and accessing related data elements by index. 2. A one-dimensional array stores elements of the same type and provides indexed access to individual elements. 3. Arrays in C++ must be declared with a size and individual elements can only be accessed by integer indices corresponding to their position in the array.

1. 1
One Dimensional Arrays

2. 2
Arrays
Arrays are Structured Data Types
They have a means of accessing
individual components
Values can be retrieved from and stored
in the structure
scores : 85 79 92 57 68 80scores : 85 79 92 57 68 80
0 1 2 3 4 5
cout << scores[2];
scores[0] = 100;
cout << scores[2];
scores[0] = 100;

3. 3
One Dimensional Array
Structured collection of components
» All of the same type
Structure given a single name
Individual elements accessed by index
indicating relative position in collection
Type of elements stored in an array can
be “just about” anything
Index of an array must be an integer

4. 4
Use of Array for Our Problem
Store elements in array as read in
Go back and access for deviations
Note declarationNote declaration

5. 5
Declaring Arrays
Syntax:
Data_type Array_name [constant];
Note declaration from our example
Tells how many elements set asideTells how many elements set aside

6. 6
Declaring Arrays
Example specifies an array…
» each element is an integer
» there is space for 100 elements
» the are numbered 0 through 99
scores : 85 79 92 57 68 80 . . .scores : 85 79 92 57 68 80 . . .
0 1 2 3 4 5 98 99

7. 7
Accessing Individual
Components
Use the name of the array
Followed by an integer expression
inside the square brackets [ ]
scores : 85 79 92 57 68 80 . . .scores : 85 79 92 57 68 80 . . .
0 1 2 3 4 5 98 99
max = scores[0];
for (x = 0; x < 100; x++)
if (scores[x] > max)
max = scores[x];
max = scores[0];
for (x = 0; x < 100; x++)
if (scores[x] > max)
max = scores[x];
Index can be:
- constant
- variable
- expression
MUST be an integer
Index can be:
- constant
- variable
- expression
MUST be an integer

8. 8
Out of Bounds Index
What happens if …
C++ does NOT check for index out of
range
Possible to walk off into “far reaches” of
memory -- clobbers ...
» other variable locations
» .exe code
» the operating system (??)
float f_list [50];
f_list [100] = 123.456;
float f_list [50];
f_list [100] = 123.456;

9. 9
Initializing Arrays in
Declarations
Possible to declare the size & initialize
Possible to omit size at declaration
» Compiler figures out size of array
int results [5] = {14, 6, 23, 8, 12 }int results [5] = {14, 6, 23, 8, 12 }
float prices [ ] = { 2.41, 85.06, 19.95, 3.91 }float prices [ ] = { 2.41, 85.06, 19.95, 3.91 }

10. 10
Aggregate Operations
Defn => an operation on the data
structure as a whole
» as opposed to operation on a SINGLE
element within the structure
Example
» would be nice to read in a WHOLE
array

11. 11
Lack of Aggregate Operations
Would be nice but . . .
C++ does NOT have . . .
Assignment operator for whole array
Arithmetic operations for whole array
(think matrix)
Comparisons for arrays (not even = =)
Return of an array type by a function

12. 12
How to Accomplish
Aggregate Operations?
Most such tasks (assignment, read,
write) can be performed some other way
» CS II course will write “classes” to
provide these functions
Otherwise
» these operations must be performed
by the programmer
» element by element in a loop

13. 13
Arrays as Parameters
This is one task that CAN be done to the
WHOLE array
C++ always passes arrays by reference

14. 14
Arrays as Parameters
The name of the array is a pointer
constant
The address of the array is passed to
the function
Size of the
array also
passed to
control loop

15. 15
Arrays as Parameters
Note the empty brackets in parameter
list
» A number can be placed here but it
will be
ignored

16. 16
Sub-array Processing
Note we specified an array size of 100
» but we don’t anticipate that many scores
Array always declared larger than needed
Must keep track of how many have been
used
» this is our limit when doing other things to
the array

17. 17
C-Strings or Character Arrays
We have learned that the elements of
an array can be just about anything
Consider an array whose elements are
all characters
» Called a C-String
» Has a collection of special routines
» Treated differently for I/O than other
types of arrays

18. 18
Declaration of C-Strings
Similar to declaration of any array
char name[30];
// no initialization
char title [20] = "Le Grande Fromage";
// initialized at declaration
// with a string
char chList [10] = {'a', 'b', 'c', 'd'};
// initialized with list of char
// values